Remove all of the duplicate numbers in an array of numbers [duplicate]












11
















This question already has an answer here:




  • Get all unique values in a JavaScript array (remove duplicates)

    66 answers




I received this question for practice and the wording confused me, as I see 2 results that it might want.



And either way, I'd like to see both solutions.



For example, if I have an array:



let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];


I'm taking this as wanting the final result as either:



let finalResult = [1, 2, 3, 4, 5, 8, 9, 10];


OR:



let finalResult = [1, 9, 10];


The difference between the two being, one just removes any duplicate numbers and leaves the rest and the second just wants any number that isn't a duplicate.



Either way, I'd like to write two functions that does one of each.



This, given by someone else gives my second solution.



let elems = {},

arr2 = arr.filter(function (e) {
if (elems[e] === undefined) {
elems[e] = true;
return true;
}
return false;
});
console.log(arr2);


I'm not sure about a function for the first one (remove all duplicates).










share|improve this question















marked as duplicate by Jared Smith, pushkin, BlueRaja - Danny Pflughoeft, the_lotus, Moira 2 days ago


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.



















  • If you're using lodash, you can use _.uniq()

    – BlueRaja - Danny Pflughoeft
    2 days ago






  • 1





    Further, this is asking for the inverse of Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array. Finally, this post is asking two separate questions and both have good answers elsewhere already.

    – Søren D. Ptæus
    2 days ago













  • To answer the question "which one is it" in a comment-answer: if you're asked to remove duplicates, I believe you should understand the first variant. The second variant removes all element that have duplicates, meaning the "original" value AND its duplicates.

    – Pierre Arlaud
    2 days ago
















11
















This question already has an answer here:




  • Get all unique values in a JavaScript array (remove duplicates)

    66 answers




I received this question for practice and the wording confused me, as I see 2 results that it might want.



And either way, I'd like to see both solutions.



For example, if I have an array:



let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];


I'm taking this as wanting the final result as either:



let finalResult = [1, 2, 3, 4, 5, 8, 9, 10];


OR:



let finalResult = [1, 9, 10];


The difference between the two being, one just removes any duplicate numbers and leaves the rest and the second just wants any number that isn't a duplicate.



Either way, I'd like to write two functions that does one of each.



This, given by someone else gives my second solution.



let elems = {},

arr2 = arr.filter(function (e) {
if (elems[e] === undefined) {
elems[e] = true;
return true;
}
return false;
});
console.log(arr2);


I'm not sure about a function for the first one (remove all duplicates).










share|improve this question















marked as duplicate by Jared Smith, pushkin, BlueRaja - Danny Pflughoeft, the_lotus, Moira 2 days ago


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.



















  • If you're using lodash, you can use _.uniq()

    – BlueRaja - Danny Pflughoeft
    2 days ago






  • 1





    Further, this is asking for the inverse of Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array. Finally, this post is asking two separate questions and both have good answers elsewhere already.

    – Søren D. Ptæus
    2 days ago













  • To answer the question "which one is it" in a comment-answer: if you're asked to remove duplicates, I believe you should understand the first variant. The second variant removes all element that have duplicates, meaning the "original" value AND its duplicates.

    – Pierre Arlaud
    2 days ago














11












11








11


2







This question already has an answer here:




  • Get all unique values in a JavaScript array (remove duplicates)

    66 answers




I received this question for practice and the wording confused me, as I see 2 results that it might want.



And either way, I'd like to see both solutions.



For example, if I have an array:



let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];


I'm taking this as wanting the final result as either:



let finalResult = [1, 2, 3, 4, 5, 8, 9, 10];


OR:



let finalResult = [1, 9, 10];


The difference between the two being, one just removes any duplicate numbers and leaves the rest and the second just wants any number that isn't a duplicate.



Either way, I'd like to write two functions that does one of each.



This, given by someone else gives my second solution.



let elems = {},

arr2 = arr.filter(function (e) {
if (elems[e] === undefined) {
elems[e] = true;
return true;
}
return false;
});
console.log(arr2);


I'm not sure about a function for the first one (remove all duplicates).










share|improve this question

















This question already has an answer here:




  • Get all unique values in a JavaScript array (remove duplicates)

    66 answers




I received this question for practice and the wording confused me, as I see 2 results that it might want.



And either way, I'd like to see both solutions.



For example, if I have an array:



let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];


I'm taking this as wanting the final result as either:



let finalResult = [1, 2, 3, 4, 5, 8, 9, 10];


OR:



let finalResult = [1, 9, 10];


The difference between the two being, one just removes any duplicate numbers and leaves the rest and the second just wants any number that isn't a duplicate.



Either way, I'd like to write two functions that does one of each.



This, given by someone else gives my second solution.



let elems = {},

arr2 = arr.filter(function (e) {
if (elems[e] === undefined) {
elems[e] = true;
return true;
}
return false;
});
console.log(arr2);


I'm not sure about a function for the first one (remove all duplicates).





This question already has an answer here:




  • Get all unique values in a JavaScript array (remove duplicates)

    66 answers








javascript arrays duplicates






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 2 days ago









pushkin

4,363112954




4,363112954










asked 2 days ago









mph85mph85

1229




1229




marked as duplicate by Jared Smith, pushkin, BlueRaja - Danny Pflughoeft, the_lotus, Moira 2 days ago


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.









marked as duplicate by Jared Smith, pushkin, BlueRaja - Danny Pflughoeft, the_lotus, Moira 2 days ago


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.















  • If you're using lodash, you can use _.uniq()

    – BlueRaja - Danny Pflughoeft
    2 days ago






  • 1





    Further, this is asking for the inverse of Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array. Finally, this post is asking two separate questions and both have good answers elsewhere already.

    – Søren D. Ptæus
    2 days ago













  • To answer the question "which one is it" in a comment-answer: if you're asked to remove duplicates, I believe you should understand the first variant. The second variant removes all element that have duplicates, meaning the "original" value AND its duplicates.

    – Pierre Arlaud
    2 days ago



















  • If you're using lodash, you can use _.uniq()

    – BlueRaja - Danny Pflughoeft
    2 days ago






  • 1





    Further, this is asking for the inverse of Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array. Finally, this post is asking two separate questions and both have good answers elsewhere already.

    – Søren D. Ptæus
    2 days ago













  • To answer the question "which one is it" in a comment-answer: if you're asked to remove duplicates, I believe you should understand the first variant. The second variant removes all element that have duplicates, meaning the "original" value AND its duplicates.

    – Pierre Arlaud
    2 days ago

















If you're using lodash, you can use _.uniq()

– BlueRaja - Danny Pflughoeft
2 days ago





If you're using lodash, you can use _.uniq()

– BlueRaja - Danny Pflughoeft
2 days ago




1




1





Further, this is asking for the inverse of Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array. Finally, this post is asking two separate questions and both have good answers elsewhere already.

– Søren D. Ptæus
2 days ago







Further, this is asking for the inverse of Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array. Finally, this post is asking two separate questions and both have good answers elsewhere already.

– Søren D. Ptæus
2 days ago















To answer the question "which one is it" in a comment-answer: if you're asked to remove duplicates, I believe you should understand the first variant. The second variant removes all element that have duplicates, meaning the "original" value AND its duplicates.

– Pierre Arlaud
2 days ago





To answer the question "which one is it" in a comment-answer: if you're asked to remove duplicates, I believe you should understand the first variant. The second variant removes all element that have duplicates, meaning the "original" value AND its duplicates.

– Pierre Arlaud
2 days ago












9 Answers
9






active

oldest

votes


















20














Using Set and Array.from()






let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

console.log(Array.from(new Set(arr)));





Alternate using regex



regex explanation here






let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

let res = arr
.join(',')
.replace(/(b,w+b)(?=.*1)/ig, '')
.split(',')
.map(Number);

console.log(res);





Alternate using objects






let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

let obj = arr.reduce((acc, val) => Object.assign(acc, {
[val]: val
}), {});

console.log(Object.values(obj));








share|improve this answer

































    14














    Just use a simple array.filter one-liner:






    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
    let finalResult = arr.filter((e, i, a) => a.indexOf(e) == i).sort(function(a, b){return a - b});
    console.log(finalResult);





    You could use another filter statement if you wanted the second result:






    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
    let finalResult = arr.filter((e, i, a) => a.filter(f => f == e).length == 1).sort(function(a, b){return a - b});
    console.log(finalResult);








    share|improve this answer


























    • You could also add .sort() to sort them by numerical order: .sort(function(a, b){return a - b}) on finalresult

      – Mukyuu
      2 days ago











    • Yes @Mukyuu, that would also be useful

      – Jack Bashford
      2 days ago






    • 5





      Worth pointing out that the run time of this approach will be quadratic on the size of the input, which is probably not great unless the input arrays are known to be always fairly small.

      – Joe Lee-Moyet
      2 days ago






    • 1





      Most voted with multiple array#filter, array#sort and array#indexOf... That is not performant

      – Yosvel Quintero
      2 days ago













    • Do note that the .sort() is not necessary - the end result without the sort is still an array without any duplicate items, just in the same order as the original array. (It does make it exactly match the finalResult variable in the question though.)

      – Florrie
      2 days ago



















    10














    For the first part you can use Set() and Spread Syntax to remove duplicates.






    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
    let res = [...new Set(arr)]
    console.log(res)





    For the second part you can use reduce()






    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
    //to get the object with count of each number in array.
    let obj = arr.reduce((ac,a) => {
    //check if number doesnot occur before then set its count to 1
    if(!ac[a]) ac[a] = 1;
    //if number is already in object increase its count
    else ac[a]++;
    return ac;
    },{})
    //Using reduce on all the keys of object means all numbers.
    let res = Object.keys(obj).reduce((ac,a) => {
    //check if count of current number 'a' is `1` in the above object then add it into array
    if(obj[a] === 1) ac.push(+a)
    return ac;
    },)
    console.log(res)








    share|improve this answer


























    • nice appreciate that, that 2nd one looks crazy. I'm assuming the time complexity for would be less than ideal compared to other results?

      – mph85
      2 days ago











    • @mph85 Yes its a little complex because it doesnot go through the array again and again instead it just store all the result obj and then filter it.Its better regarding performance

      – Maheer Ali
      2 days ago













    • could you remind me why we need the spread operator? what happens if we don't have it? @Maheer Ali

      – mph85
      2 days ago













    • Is it because if we don't have it, it'll just log an object?

      – mph85
      2 days ago











    • @mph85 No if we will not have it. We will have a Set() inside array. We use it convert Set() to Array

      – Maheer Ali
      2 days ago



















    5














    You could sort the array before and filter the array by checking only one side for duplicates or both sides.






    var array = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10],
    result1,
    result2;

    array.sort((a, b) => a - b);

    result1 = array.filter((v, i, a) => a[i - 1] !== v);
    result2 = array.filter((v, i, a) => a[i - 1] !== v && a[i + 1] !== v);

    console.log(...result1);
    console.log(...result2)








    share|improve this answer
























    • thank for that, for the result1 what is going on with the a[i - 1] !== v?

      – mph85
      2 days ago











    • a is the array, i is the actual index, and v is the actual value. it takes the value from the index before of the actual index and looks if the values are not equal.

      – Nina Scholz
      2 days ago











    • ah ok, and sorry, it takes the value from the index before of the actual index? Not sure what you mean by that

      – mph85
      2 days ago













    • for example if you have the value 9 of the array as v, then the value before is 8.

      – Nina Scholz
      2 days ago











    • ah ok, thank you for that

      – mph85
      2 days ago





















    5














    You can create both arrays in One Go






    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
    let unique = new Set();
    let repeated = Array.from(arr.reduce((acc, curr) => {
    acc.has(curr) ? unique.delete(curr) : acc.add(curr) && unique.add(curr);
    return acc;
    }, new Set()));

    console.log(Array.from(unique))
    console.log(repeated)








    share|improve this answer



















    • 1





      Nice one mate +1

      – Maheer Ali
      2 days ago











    • I wonder if the ternary plus && could be unclear though (x?y:z&&w)? It's not obvious to me how JS's order of operations would handle that, and I wonder if you could get across the same logic and reasoning by using if/else?

      – Florrie
      2 days ago



















    5














    You can use Array.prototype.reduce() create a hash object where the keys are the numbers in the array and the values are going to be the the repeated occurrence of numbers in the arr array variable..



    Then using Object.keys():




    • Remove all duplicates Object.keys(hash)

    • Remove all duplicates but filtering with Array.prototype.filter() to get the numbers with only one occurrence


    Code:






    const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
    const hash = arr.reduce((a, c) => (a[c] = (a[c] || 0) + 1, a), {});

    // [1, 2, 3, 4, 5, 8, 9, 10];
    const finalResultOne = Object.keys(hash);

    // [1, 9, 10];
    const finalResultTwo = Object.keys(hash).filter(k => hash[k] === 1);

    console.log('finalResultOne:', ...finalResultOne);
    console.log('finalResultTwo:', ...finalResultTwo);








    share|improve this answer

































      4














      You can use closure and Map






      let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

      const build = ar => {
      const mapObj = ar.reduce((acc, e) => {
      acc.has(e) ? acc.set(e, true) : acc.set(e, false)
      return acc
      }, new Map())

      return function(hasDup = true) {
      if(hasDup) return [...mapObj.keys()]
      else return [...mapObj].filter(([key, val]) => !val).map(([k, v])=> k)
      }
      }

      const getArr = build(arr)

      console.log(getArr())
      console.log(getArr(false))








      share|improve this answer































        4














        As many other have said, the first one is just [...new Set(arr)]



        For the second, just filter out those that occur more than once:




        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

        const count = (arr, e) => arr.filter(n => n == e).length

        const unique = arr => arr.filter(e => count(arr, e) < 2)

        console.log(unique(arr));








        share|improve this answer































          2

















          var arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
          var map = {};
          var finalResult = ;
          for (var i = 0; i < arr.length; i++) {
          if (!map.hasOwnProperty(arr[i])) {
          map[arr[i]] = true;
          finalResult.push(arr[i]);
          }
          }

          //if you need it sorted otherwise it will be in order
          finalResult.sort(function(a, b) {
          return a - b
          });

          console.log(finalResult);








          share|improve this answer
































            9 Answers
            9






            active

            oldest

            votes








            9 Answers
            9






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            20














            Using Set and Array.from()






            let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

            console.log(Array.from(new Set(arr)));





            Alternate using regex



            regex explanation here






            let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

            let res = arr
            .join(',')
            .replace(/(b,w+b)(?=.*1)/ig, '')
            .split(',')
            .map(Number);

            console.log(res);





            Alternate using objects






            let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

            let obj = arr.reduce((acc, val) => Object.assign(acc, {
            [val]: val
            }), {});

            console.log(Object.values(obj));








            share|improve this answer






























              20














              Using Set and Array.from()






              let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

              console.log(Array.from(new Set(arr)));





              Alternate using regex



              regex explanation here






              let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

              let res = arr
              .join(',')
              .replace(/(b,w+b)(?=.*1)/ig, '')
              .split(',')
              .map(Number);

              console.log(res);





              Alternate using objects






              let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

              let obj = arr.reduce((acc, val) => Object.assign(acc, {
              [val]: val
              }), {});

              console.log(Object.values(obj));








              share|improve this answer




























                20












                20








                20







                Using Set and Array.from()






                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                console.log(Array.from(new Set(arr)));





                Alternate using regex



                regex explanation here






                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let res = arr
                .join(',')
                .replace(/(b,w+b)(?=.*1)/ig, '')
                .split(',')
                .map(Number);

                console.log(res);





                Alternate using objects






                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let obj = arr.reduce((acc, val) => Object.assign(acc, {
                [val]: val
                }), {});

                console.log(Object.values(obj));








                share|improve this answer















                Using Set and Array.from()






                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                console.log(Array.from(new Set(arr)));





                Alternate using regex



                regex explanation here






                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let res = arr
                .join(',')
                .replace(/(b,w+b)(?=.*1)/ig, '')
                .split(',')
                .map(Number);

                console.log(res);





                Alternate using objects






                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let obj = arr.reduce((acc, val) => Object.assign(acc, {
                [val]: val
                }), {});

                console.log(Object.values(obj));








                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                console.log(Array.from(new Set(arr)));





                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                console.log(Array.from(new Set(arr)));





                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let res = arr
                .join(',')
                .replace(/(b,w+b)(?=.*1)/ig, '')
                .split(',')
                .map(Number);

                console.log(res);





                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let res = arr
                .join(',')
                .replace(/(b,w+b)(?=.*1)/ig, '')
                .split(',')
                .map(Number);

                console.log(res);





                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let obj = arr.reduce((acc, val) => Object.assign(acc, {
                [val]: val
                }), {});

                console.log(Object.values(obj));





                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                let obj = arr.reduce((acc, val) => Object.assign(acc, {
                [val]: val
                }), {});

                console.log(Object.values(obj));






                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited 2 days ago

























                answered 2 days ago









                Aswin KumarAswin Kumar

                919115




                919115

























                    14














                    Just use a simple array.filter one-liner:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.indexOf(e) == i).sort(function(a, b){return a - b});
                    console.log(finalResult);





                    You could use another filter statement if you wanted the second result:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.filter(f => f == e).length == 1).sort(function(a, b){return a - b});
                    console.log(finalResult);








                    share|improve this answer


























                    • You could also add .sort() to sort them by numerical order: .sort(function(a, b){return a - b}) on finalresult

                      – Mukyuu
                      2 days ago











                    • Yes @Mukyuu, that would also be useful

                      – Jack Bashford
                      2 days ago






                    • 5





                      Worth pointing out that the run time of this approach will be quadratic on the size of the input, which is probably not great unless the input arrays are known to be always fairly small.

                      – Joe Lee-Moyet
                      2 days ago






                    • 1





                      Most voted with multiple array#filter, array#sort and array#indexOf... That is not performant

                      – Yosvel Quintero
                      2 days ago













                    • Do note that the .sort() is not necessary - the end result without the sort is still an array without any duplicate items, just in the same order as the original array. (It does make it exactly match the finalResult variable in the question though.)

                      – Florrie
                      2 days ago
















                    14














                    Just use a simple array.filter one-liner:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.indexOf(e) == i).sort(function(a, b){return a - b});
                    console.log(finalResult);





                    You could use another filter statement if you wanted the second result:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.filter(f => f == e).length == 1).sort(function(a, b){return a - b});
                    console.log(finalResult);








                    share|improve this answer


























                    • You could also add .sort() to sort them by numerical order: .sort(function(a, b){return a - b}) on finalresult

                      – Mukyuu
                      2 days ago











                    • Yes @Mukyuu, that would also be useful

                      – Jack Bashford
                      2 days ago






                    • 5





                      Worth pointing out that the run time of this approach will be quadratic on the size of the input, which is probably not great unless the input arrays are known to be always fairly small.

                      – Joe Lee-Moyet
                      2 days ago






                    • 1





                      Most voted with multiple array#filter, array#sort and array#indexOf... That is not performant

                      – Yosvel Quintero
                      2 days ago













                    • Do note that the .sort() is not necessary - the end result without the sort is still an array without any duplicate items, just in the same order as the original array. (It does make it exactly match the finalResult variable in the question though.)

                      – Florrie
                      2 days ago














                    14












                    14








                    14







                    Just use a simple array.filter one-liner:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.indexOf(e) == i).sort(function(a, b){return a - b});
                    console.log(finalResult);





                    You could use another filter statement if you wanted the second result:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.filter(f => f == e).length == 1).sort(function(a, b){return a - b});
                    console.log(finalResult);








                    share|improve this answer















                    Just use a simple array.filter one-liner:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.indexOf(e) == i).sort(function(a, b){return a - b});
                    console.log(finalResult);





                    You could use another filter statement if you wanted the second result:






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.filter(f => f == e).length == 1).sort(function(a, b){return a - b});
                    console.log(finalResult);








                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.indexOf(e) == i).sort(function(a, b){return a - b});
                    console.log(finalResult);





                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.indexOf(e) == i).sort(function(a, b){return a - b});
                    console.log(finalResult);





                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.filter(f => f == e).length == 1).sort(function(a, b){return a - b});
                    console.log(finalResult);





                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let finalResult = arr.filter((e, i, a) => a.filter(f => f == e).length == 1).sort(function(a, b){return a - b});
                    console.log(finalResult);






                    share|improve this answer














                    share|improve this answer



                    share|improve this answer








                    edited 2 days ago









                    Mukyuu

                    1,82431123




                    1,82431123










                    answered 2 days ago









                    Jack BashfordJack Bashford

                    12.8k31847




                    12.8k31847













                    • You could also add .sort() to sort them by numerical order: .sort(function(a, b){return a - b}) on finalresult

                      – Mukyuu
                      2 days ago











                    • Yes @Mukyuu, that would also be useful

                      – Jack Bashford
                      2 days ago






                    • 5





                      Worth pointing out that the run time of this approach will be quadratic on the size of the input, which is probably not great unless the input arrays are known to be always fairly small.

                      – Joe Lee-Moyet
                      2 days ago






                    • 1





                      Most voted with multiple array#filter, array#sort and array#indexOf... That is not performant

                      – Yosvel Quintero
                      2 days ago













                    • Do note that the .sort() is not necessary - the end result without the sort is still an array without any duplicate items, just in the same order as the original array. (It does make it exactly match the finalResult variable in the question though.)

                      – Florrie
                      2 days ago



















                    • You could also add .sort() to sort them by numerical order: .sort(function(a, b){return a - b}) on finalresult

                      – Mukyuu
                      2 days ago











                    • Yes @Mukyuu, that would also be useful

                      – Jack Bashford
                      2 days ago






                    • 5





                      Worth pointing out that the run time of this approach will be quadratic on the size of the input, which is probably not great unless the input arrays are known to be always fairly small.

                      – Joe Lee-Moyet
                      2 days ago






                    • 1





                      Most voted with multiple array#filter, array#sort and array#indexOf... That is not performant

                      – Yosvel Quintero
                      2 days ago













                    • Do note that the .sort() is not necessary - the end result without the sort is still an array without any duplicate items, just in the same order as the original array. (It does make it exactly match the finalResult variable in the question though.)

                      – Florrie
                      2 days ago

















                    You could also add .sort() to sort them by numerical order: .sort(function(a, b){return a - b}) on finalresult

                    – Mukyuu
                    2 days ago





                    You could also add .sort() to sort them by numerical order: .sort(function(a, b){return a - b}) on finalresult

                    – Mukyuu
                    2 days ago













                    Yes @Mukyuu, that would also be useful

                    – Jack Bashford
                    2 days ago





                    Yes @Mukyuu, that would also be useful

                    – Jack Bashford
                    2 days ago




                    5




                    5





                    Worth pointing out that the run time of this approach will be quadratic on the size of the input, which is probably not great unless the input arrays are known to be always fairly small.

                    – Joe Lee-Moyet
                    2 days ago





                    Worth pointing out that the run time of this approach will be quadratic on the size of the input, which is probably not great unless the input arrays are known to be always fairly small.

                    – Joe Lee-Moyet
                    2 days ago




                    1




                    1





                    Most voted with multiple array#filter, array#sort and array#indexOf... That is not performant

                    – Yosvel Quintero
                    2 days ago







                    Most voted with multiple array#filter, array#sort and array#indexOf... That is not performant

                    – Yosvel Quintero
                    2 days ago















                    Do note that the .sort() is not necessary - the end result without the sort is still an array without any duplicate items, just in the same order as the original array. (It does make it exactly match the finalResult variable in the question though.)

                    – Florrie
                    2 days ago





                    Do note that the .sort() is not necessary - the end result without the sort is still an array without any duplicate items, just in the same order as the original array. (It does make it exactly match the finalResult variable in the question though.)

                    – Florrie
                    2 days ago











                    10














                    For the first part you can use Set() and Spread Syntax to remove duplicates.






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let res = [...new Set(arr)]
                    console.log(res)





                    For the second part you can use reduce()






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    //to get the object with count of each number in array.
                    let obj = arr.reduce((ac,a) => {
                    //check if number doesnot occur before then set its count to 1
                    if(!ac[a]) ac[a] = 1;
                    //if number is already in object increase its count
                    else ac[a]++;
                    return ac;
                    },{})
                    //Using reduce on all the keys of object means all numbers.
                    let res = Object.keys(obj).reduce((ac,a) => {
                    //check if count of current number 'a' is `1` in the above object then add it into array
                    if(obj[a] === 1) ac.push(+a)
                    return ac;
                    },)
                    console.log(res)








                    share|improve this answer


























                    • nice appreciate that, that 2nd one looks crazy. I'm assuming the time complexity for would be less than ideal compared to other results?

                      – mph85
                      2 days ago











                    • @mph85 Yes its a little complex because it doesnot go through the array again and again instead it just store all the result obj and then filter it.Its better regarding performance

                      – Maheer Ali
                      2 days ago













                    • could you remind me why we need the spread operator? what happens if we don't have it? @Maheer Ali

                      – mph85
                      2 days ago













                    • Is it because if we don't have it, it'll just log an object?

                      – mph85
                      2 days ago











                    • @mph85 No if we will not have it. We will have a Set() inside array. We use it convert Set() to Array

                      – Maheer Ali
                      2 days ago
















                    10














                    For the first part you can use Set() and Spread Syntax to remove duplicates.






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let res = [...new Set(arr)]
                    console.log(res)





                    For the second part you can use reduce()






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    //to get the object with count of each number in array.
                    let obj = arr.reduce((ac,a) => {
                    //check if number doesnot occur before then set its count to 1
                    if(!ac[a]) ac[a] = 1;
                    //if number is already in object increase its count
                    else ac[a]++;
                    return ac;
                    },{})
                    //Using reduce on all the keys of object means all numbers.
                    let res = Object.keys(obj).reduce((ac,a) => {
                    //check if count of current number 'a' is `1` in the above object then add it into array
                    if(obj[a] === 1) ac.push(+a)
                    return ac;
                    },)
                    console.log(res)








                    share|improve this answer


























                    • nice appreciate that, that 2nd one looks crazy. I'm assuming the time complexity for would be less than ideal compared to other results?

                      – mph85
                      2 days ago











                    • @mph85 Yes its a little complex because it doesnot go through the array again and again instead it just store all the result obj and then filter it.Its better regarding performance

                      – Maheer Ali
                      2 days ago













                    • could you remind me why we need the spread operator? what happens if we don't have it? @Maheer Ali

                      – mph85
                      2 days ago













                    • Is it because if we don't have it, it'll just log an object?

                      – mph85
                      2 days ago











                    • @mph85 No if we will not have it. We will have a Set() inside array. We use it convert Set() to Array

                      – Maheer Ali
                      2 days ago














                    10












                    10








                    10







                    For the first part you can use Set() and Spread Syntax to remove duplicates.






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let res = [...new Set(arr)]
                    console.log(res)





                    For the second part you can use reduce()






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    //to get the object with count of each number in array.
                    let obj = arr.reduce((ac,a) => {
                    //check if number doesnot occur before then set its count to 1
                    if(!ac[a]) ac[a] = 1;
                    //if number is already in object increase its count
                    else ac[a]++;
                    return ac;
                    },{})
                    //Using reduce on all the keys of object means all numbers.
                    let res = Object.keys(obj).reduce((ac,a) => {
                    //check if count of current number 'a' is `1` in the above object then add it into array
                    if(obj[a] === 1) ac.push(+a)
                    return ac;
                    },)
                    console.log(res)








                    share|improve this answer















                    For the first part you can use Set() and Spread Syntax to remove duplicates.






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let res = [...new Set(arr)]
                    console.log(res)





                    For the second part you can use reduce()






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    //to get the object with count of each number in array.
                    let obj = arr.reduce((ac,a) => {
                    //check if number doesnot occur before then set its count to 1
                    if(!ac[a]) ac[a] = 1;
                    //if number is already in object increase its count
                    else ac[a]++;
                    return ac;
                    },{})
                    //Using reduce on all the keys of object means all numbers.
                    let res = Object.keys(obj).reduce((ac,a) => {
                    //check if count of current number 'a' is `1` in the above object then add it into array
                    if(obj[a] === 1) ac.push(+a)
                    return ac;
                    },)
                    console.log(res)








                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let res = [...new Set(arr)]
                    console.log(res)





                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let res = [...new Set(arr)]
                    console.log(res)





                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    //to get the object with count of each number in array.
                    let obj = arr.reduce((ac,a) => {
                    //check if number doesnot occur before then set its count to 1
                    if(!ac[a]) ac[a] = 1;
                    //if number is already in object increase its count
                    else ac[a]++;
                    return ac;
                    },{})
                    //Using reduce on all the keys of object means all numbers.
                    let res = Object.keys(obj).reduce((ac,a) => {
                    //check if count of current number 'a' is `1` in the above object then add it into array
                    if(obj[a] === 1) ac.push(+a)
                    return ac;
                    },)
                    console.log(res)





                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    //to get the object with count of each number in array.
                    let obj = arr.reduce((ac,a) => {
                    //check if number doesnot occur before then set its count to 1
                    if(!ac[a]) ac[a] = 1;
                    //if number is already in object increase its count
                    else ac[a]++;
                    return ac;
                    },{})
                    //Using reduce on all the keys of object means all numbers.
                    let res = Object.keys(obj).reduce((ac,a) => {
                    //check if count of current number 'a' is `1` in the above object then add it into array
                    if(obj[a] === 1) ac.push(+a)
                    return ac;
                    },)
                    console.log(res)






                    share|improve this answer














                    share|improve this answer



                    share|improve this answer








                    edited 2 days ago

























                    answered 2 days ago









                    Maheer AliMaheer Ali

                    6,963518




                    6,963518













                    • nice appreciate that, that 2nd one looks crazy. I'm assuming the time complexity for would be less than ideal compared to other results?

                      – mph85
                      2 days ago











                    • @mph85 Yes its a little complex because it doesnot go through the array again and again instead it just store all the result obj and then filter it.Its better regarding performance

                      – Maheer Ali
                      2 days ago













                    • could you remind me why we need the spread operator? what happens if we don't have it? @Maheer Ali

                      – mph85
                      2 days ago













                    • Is it because if we don't have it, it'll just log an object?

                      – mph85
                      2 days ago











                    • @mph85 No if we will not have it. We will have a Set() inside array. We use it convert Set() to Array

                      – Maheer Ali
                      2 days ago



















                    • nice appreciate that, that 2nd one looks crazy. I'm assuming the time complexity for would be less than ideal compared to other results?

                      – mph85
                      2 days ago











                    • @mph85 Yes its a little complex because it doesnot go through the array again and again instead it just store all the result obj and then filter it.Its better regarding performance

                      – Maheer Ali
                      2 days ago













                    • could you remind me why we need the spread operator? what happens if we don't have it? @Maheer Ali

                      – mph85
                      2 days ago













                    • Is it because if we don't have it, it'll just log an object?

                      – mph85
                      2 days ago











                    • @mph85 No if we will not have it. We will have a Set() inside array. We use it convert Set() to Array

                      – Maheer Ali
                      2 days ago

















                    nice appreciate that, that 2nd one looks crazy. I'm assuming the time complexity for would be less than ideal compared to other results?

                    – mph85
                    2 days ago





                    nice appreciate that, that 2nd one looks crazy. I'm assuming the time complexity for would be less than ideal compared to other results?

                    – mph85
                    2 days ago













                    @mph85 Yes its a little complex because it doesnot go through the array again and again instead it just store all the result obj and then filter it.Its better regarding performance

                    – Maheer Ali
                    2 days ago







                    @mph85 Yes its a little complex because it doesnot go through the array again and again instead it just store all the result obj and then filter it.Its better regarding performance

                    – Maheer Ali
                    2 days ago















                    could you remind me why we need the spread operator? what happens if we don't have it? @Maheer Ali

                    – mph85
                    2 days ago







                    could you remind me why we need the spread operator? what happens if we don't have it? @Maheer Ali

                    – mph85
                    2 days ago















                    Is it because if we don't have it, it'll just log an object?

                    – mph85
                    2 days ago





                    Is it because if we don't have it, it'll just log an object?

                    – mph85
                    2 days ago













                    @mph85 No if we will not have it. We will have a Set() inside array. We use it convert Set() to Array

                    – Maheer Ali
                    2 days ago





                    @mph85 No if we will not have it. We will have a Set() inside array. We use it convert Set() to Array

                    – Maheer Ali
                    2 days ago











                    5














                    You could sort the array before and filter the array by checking only one side for duplicates or both sides.






                    var array = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10],
                    result1,
                    result2;

                    array.sort((a, b) => a - b);

                    result1 = array.filter((v, i, a) => a[i - 1] !== v);
                    result2 = array.filter((v, i, a) => a[i - 1] !== v && a[i + 1] !== v);

                    console.log(...result1);
                    console.log(...result2)








                    share|improve this answer
























                    • thank for that, for the result1 what is going on with the a[i - 1] !== v?

                      – mph85
                      2 days ago











                    • a is the array, i is the actual index, and v is the actual value. it takes the value from the index before of the actual index and looks if the values are not equal.

                      – Nina Scholz
                      2 days ago











                    • ah ok, and sorry, it takes the value from the index before of the actual index? Not sure what you mean by that

                      – mph85
                      2 days ago













                    • for example if you have the value 9 of the array as v, then the value before is 8.

                      – Nina Scholz
                      2 days ago











                    • ah ok, thank you for that

                      – mph85
                      2 days ago


















                    5














                    You could sort the array before and filter the array by checking only one side for duplicates or both sides.






                    var array = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10],
                    result1,
                    result2;

                    array.sort((a, b) => a - b);

                    result1 = array.filter((v, i, a) => a[i - 1] !== v);
                    result2 = array.filter((v, i, a) => a[i - 1] !== v && a[i + 1] !== v);

                    console.log(...result1);
                    console.log(...result2)








                    share|improve this answer
























                    • thank for that, for the result1 what is going on with the a[i - 1] !== v?

                      – mph85
                      2 days ago











                    • a is the array, i is the actual index, and v is the actual value. it takes the value from the index before of the actual index and looks if the values are not equal.

                      – Nina Scholz
                      2 days ago











                    • ah ok, and sorry, it takes the value from the index before of the actual index? Not sure what you mean by that

                      – mph85
                      2 days ago













                    • for example if you have the value 9 of the array as v, then the value before is 8.

                      – Nina Scholz
                      2 days ago











                    • ah ok, thank you for that

                      – mph85
                      2 days ago
















                    5












                    5








                    5







                    You could sort the array before and filter the array by checking only one side for duplicates or both sides.






                    var array = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10],
                    result1,
                    result2;

                    array.sort((a, b) => a - b);

                    result1 = array.filter((v, i, a) => a[i - 1] !== v);
                    result2 = array.filter((v, i, a) => a[i - 1] !== v && a[i + 1] !== v);

                    console.log(...result1);
                    console.log(...result2)








                    share|improve this answer













                    You could sort the array before and filter the array by checking only one side for duplicates or both sides.






                    var array = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10],
                    result1,
                    result2;

                    array.sort((a, b) => a - b);

                    result1 = array.filter((v, i, a) => a[i - 1] !== v);
                    result2 = array.filter((v, i, a) => a[i - 1] !== v && a[i + 1] !== v);

                    console.log(...result1);
                    console.log(...result2)








                    var array = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10],
                    result1,
                    result2;

                    array.sort((a, b) => a - b);

                    result1 = array.filter((v, i, a) => a[i - 1] !== v);
                    result2 = array.filter((v, i, a) => a[i - 1] !== v && a[i + 1] !== v);

                    console.log(...result1);
                    console.log(...result2)





                    var array = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10],
                    result1,
                    result2;

                    array.sort((a, b) => a - b);

                    result1 = array.filter((v, i, a) => a[i - 1] !== v);
                    result2 = array.filter((v, i, a) => a[i - 1] !== v && a[i + 1] !== v);

                    console.log(...result1);
                    console.log(...result2)






                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered 2 days ago









                    Nina ScholzNina Scholz

                    193k15104177




                    193k15104177













                    • thank for that, for the result1 what is going on with the a[i - 1] !== v?

                      – mph85
                      2 days ago











                    • a is the array, i is the actual index, and v is the actual value. it takes the value from the index before of the actual index and looks if the values are not equal.

                      – Nina Scholz
                      2 days ago











                    • ah ok, and sorry, it takes the value from the index before of the actual index? Not sure what you mean by that

                      – mph85
                      2 days ago













                    • for example if you have the value 9 of the array as v, then the value before is 8.

                      – Nina Scholz
                      2 days ago











                    • ah ok, thank you for that

                      – mph85
                      2 days ago





















                    • thank for that, for the result1 what is going on with the a[i - 1] !== v?

                      – mph85
                      2 days ago











                    • a is the array, i is the actual index, and v is the actual value. it takes the value from the index before of the actual index and looks if the values are not equal.

                      – Nina Scholz
                      2 days ago











                    • ah ok, and sorry, it takes the value from the index before of the actual index? Not sure what you mean by that

                      – mph85
                      2 days ago













                    • for example if you have the value 9 of the array as v, then the value before is 8.

                      – Nina Scholz
                      2 days ago











                    • ah ok, thank you for that

                      – mph85
                      2 days ago



















                    thank for that, for the result1 what is going on with the a[i - 1] !== v?

                    – mph85
                    2 days ago





                    thank for that, for the result1 what is going on with the a[i - 1] !== v?

                    – mph85
                    2 days ago













                    a is the array, i is the actual index, and v is the actual value. it takes the value from the index before of the actual index and looks if the values are not equal.

                    – Nina Scholz
                    2 days ago





                    a is the array, i is the actual index, and v is the actual value. it takes the value from the index before of the actual index and looks if the values are not equal.

                    – Nina Scholz
                    2 days ago













                    ah ok, and sorry, it takes the value from the index before of the actual index? Not sure what you mean by that

                    – mph85
                    2 days ago







                    ah ok, and sorry, it takes the value from the index before of the actual index? Not sure what you mean by that

                    – mph85
                    2 days ago















                    for example if you have the value 9 of the array as v, then the value before is 8.

                    – Nina Scholz
                    2 days ago





                    for example if you have the value 9 of the array as v, then the value before is 8.

                    – Nina Scholz
                    2 days ago













                    ah ok, thank you for that

                    – mph85
                    2 days ago







                    ah ok, thank you for that

                    – mph85
                    2 days ago













                    5














                    You can create both arrays in One Go






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let unique = new Set();
                    let repeated = Array.from(arr.reduce((acc, curr) => {
                    acc.has(curr) ? unique.delete(curr) : acc.add(curr) && unique.add(curr);
                    return acc;
                    }, new Set()));

                    console.log(Array.from(unique))
                    console.log(repeated)








                    share|improve this answer



















                    • 1





                      Nice one mate +1

                      – Maheer Ali
                      2 days ago











                    • I wonder if the ternary plus && could be unclear though (x?y:z&&w)? It's not obvious to me how JS's order of operations would handle that, and I wonder if you could get across the same logic and reasoning by using if/else?

                      – Florrie
                      2 days ago
















                    5














                    You can create both arrays in One Go






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let unique = new Set();
                    let repeated = Array.from(arr.reduce((acc, curr) => {
                    acc.has(curr) ? unique.delete(curr) : acc.add(curr) && unique.add(curr);
                    return acc;
                    }, new Set()));

                    console.log(Array.from(unique))
                    console.log(repeated)








                    share|improve this answer



















                    • 1





                      Nice one mate +1

                      – Maheer Ali
                      2 days ago











                    • I wonder if the ternary plus && could be unclear though (x?y:z&&w)? It's not obvious to me how JS's order of operations would handle that, and I wonder if you could get across the same logic and reasoning by using if/else?

                      – Florrie
                      2 days ago














                    5












                    5








                    5







                    You can create both arrays in One Go






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let unique = new Set();
                    let repeated = Array.from(arr.reduce((acc, curr) => {
                    acc.has(curr) ? unique.delete(curr) : acc.add(curr) && unique.add(curr);
                    return acc;
                    }, new Set()));

                    console.log(Array.from(unique))
                    console.log(repeated)








                    share|improve this answer













                    You can create both arrays in One Go






                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let unique = new Set();
                    let repeated = Array.from(arr.reduce((acc, curr) => {
                    acc.has(curr) ? unique.delete(curr) : acc.add(curr) && unique.add(curr);
                    return acc;
                    }, new Set()));

                    console.log(Array.from(unique))
                    console.log(repeated)








                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let unique = new Set();
                    let repeated = Array.from(arr.reduce((acc, curr) => {
                    acc.has(curr) ? unique.delete(curr) : acc.add(curr) && unique.add(curr);
                    return acc;
                    }, new Set()));

                    console.log(Array.from(unique))
                    console.log(repeated)





                    let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    let unique = new Set();
                    let repeated = Array.from(arr.reduce((acc, curr) => {
                    acc.has(curr) ? unique.delete(curr) : acc.add(curr) && unique.add(curr);
                    return acc;
                    }, new Set()));

                    console.log(Array.from(unique))
                    console.log(repeated)






                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered 2 days ago









                    AZ_AZ_

                    598210




                    598210








                    • 1





                      Nice one mate +1

                      – Maheer Ali
                      2 days ago











                    • I wonder if the ternary plus && could be unclear though (x?y:z&&w)? It's not obvious to me how JS's order of operations would handle that, and I wonder if you could get across the same logic and reasoning by using if/else?

                      – Florrie
                      2 days ago














                    • 1





                      Nice one mate +1

                      – Maheer Ali
                      2 days ago











                    • I wonder if the ternary plus && could be unclear though (x?y:z&&w)? It's not obvious to me how JS's order of operations would handle that, and I wonder if you could get across the same logic and reasoning by using if/else?

                      – Florrie
                      2 days ago








                    1




                    1





                    Nice one mate +1

                    – Maheer Ali
                    2 days ago





                    Nice one mate +1

                    – Maheer Ali
                    2 days ago













                    I wonder if the ternary plus && could be unclear though (x?y:z&&w)? It's not obvious to me how JS's order of operations would handle that, and I wonder if you could get across the same logic and reasoning by using if/else?

                    – Florrie
                    2 days ago





                    I wonder if the ternary plus && could be unclear though (x?y:z&&w)? It's not obvious to me how JS's order of operations would handle that, and I wonder if you could get across the same logic and reasoning by using if/else?

                    – Florrie
                    2 days ago











                    5














                    You can use Array.prototype.reduce() create a hash object where the keys are the numbers in the array and the values are going to be the the repeated occurrence of numbers in the arr array variable..



                    Then using Object.keys():




                    • Remove all duplicates Object.keys(hash)

                    • Remove all duplicates but filtering with Array.prototype.filter() to get the numbers with only one occurrence


                    Code:






                    const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                    const hash = arr.reduce((a, c) => (a[c] = (a[c] || 0) + 1, a), {});

                    // [1, 2, 3, 4, 5, 8, 9, 10];
                    const finalResultOne = Object.keys(hash);

                    // [1, 9, 10];
                    const finalResultTwo = Object.keys(hash).filter(k => hash[k] === 1);

                    console.log('finalResultOne:', ...finalResultOne);
                    console.log('finalResultTwo:', ...finalResultTwo);








                    share|improve this answer






























                      5














                      You can use Array.prototype.reduce() create a hash object where the keys are the numbers in the array and the values are going to be the the repeated occurrence of numbers in the arr array variable..



                      Then using Object.keys():




                      • Remove all duplicates Object.keys(hash)

                      • Remove all duplicates but filtering with Array.prototype.filter() to get the numbers with only one occurrence


                      Code:






                      const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                      const hash = arr.reduce((a, c) => (a[c] = (a[c] || 0) + 1, a), {});

                      // [1, 2, 3, 4, 5, 8, 9, 10];
                      const finalResultOne = Object.keys(hash);

                      // [1, 9, 10];
                      const finalResultTwo = Object.keys(hash).filter(k => hash[k] === 1);

                      console.log('finalResultOne:', ...finalResultOne);
                      console.log('finalResultTwo:', ...finalResultTwo);








                      share|improve this answer




























                        5












                        5








                        5







                        You can use Array.prototype.reduce() create a hash object where the keys are the numbers in the array and the values are going to be the the repeated occurrence of numbers in the arr array variable..



                        Then using Object.keys():




                        • Remove all duplicates Object.keys(hash)

                        • Remove all duplicates but filtering with Array.prototype.filter() to get the numbers with only one occurrence


                        Code:






                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                        const hash = arr.reduce((a, c) => (a[c] = (a[c] || 0) + 1, a), {});

                        // [1, 2, 3, 4, 5, 8, 9, 10];
                        const finalResultOne = Object.keys(hash);

                        // [1, 9, 10];
                        const finalResultTwo = Object.keys(hash).filter(k => hash[k] === 1);

                        console.log('finalResultOne:', ...finalResultOne);
                        console.log('finalResultTwo:', ...finalResultTwo);








                        share|improve this answer















                        You can use Array.prototype.reduce() create a hash object where the keys are the numbers in the array and the values are going to be the the repeated occurrence of numbers in the arr array variable..



                        Then using Object.keys():




                        • Remove all duplicates Object.keys(hash)

                        • Remove all duplicates but filtering with Array.prototype.filter() to get the numbers with only one occurrence


                        Code:






                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                        const hash = arr.reduce((a, c) => (a[c] = (a[c] || 0) + 1, a), {});

                        // [1, 2, 3, 4, 5, 8, 9, 10];
                        const finalResultOne = Object.keys(hash);

                        // [1, 9, 10];
                        const finalResultTwo = Object.keys(hash).filter(k => hash[k] === 1);

                        console.log('finalResultOne:', ...finalResultOne);
                        console.log('finalResultTwo:', ...finalResultTwo);








                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                        const hash = arr.reduce((a, c) => (a[c] = (a[c] || 0) + 1, a), {});

                        // [1, 2, 3, 4, 5, 8, 9, 10];
                        const finalResultOne = Object.keys(hash);

                        // [1, 9, 10];
                        const finalResultTwo = Object.keys(hash).filter(k => hash[k] === 1);

                        console.log('finalResultOne:', ...finalResultOne);
                        console.log('finalResultTwo:', ...finalResultTwo);





                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                        const hash = arr.reduce((a, c) => (a[c] = (a[c] || 0) + 1, a), {});

                        // [1, 2, 3, 4, 5, 8, 9, 10];
                        const finalResultOne = Object.keys(hash);

                        // [1, 9, 10];
                        const finalResultTwo = Object.keys(hash).filter(k => hash[k] === 1);

                        console.log('finalResultOne:', ...finalResultOne);
                        console.log('finalResultTwo:', ...finalResultTwo);






                        share|improve this answer














                        share|improve this answer



                        share|improve this answer








                        edited 2 days ago

























                        answered 2 days ago









                        Yosvel QuinteroYosvel Quintero

                        11.8k42531




                        11.8k42531























                            4














                            You can use closure and Map






                            let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                            const build = ar => {
                            const mapObj = ar.reduce((acc, e) => {
                            acc.has(e) ? acc.set(e, true) : acc.set(e, false)
                            return acc
                            }, new Map())

                            return function(hasDup = true) {
                            if(hasDup) return [...mapObj.keys()]
                            else return [...mapObj].filter(([key, val]) => !val).map(([k, v])=> k)
                            }
                            }

                            const getArr = build(arr)

                            console.log(getArr())
                            console.log(getArr(false))








                            share|improve this answer




























                              4














                              You can use closure and Map






                              let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                              const build = ar => {
                              const mapObj = ar.reduce((acc, e) => {
                              acc.has(e) ? acc.set(e, true) : acc.set(e, false)
                              return acc
                              }, new Map())

                              return function(hasDup = true) {
                              if(hasDup) return [...mapObj.keys()]
                              else return [...mapObj].filter(([key, val]) => !val).map(([k, v])=> k)
                              }
                              }

                              const getArr = build(arr)

                              console.log(getArr())
                              console.log(getArr(false))








                              share|improve this answer


























                                4












                                4








                                4







                                You can use closure and Map






                                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                const build = ar => {
                                const mapObj = ar.reduce((acc, e) => {
                                acc.has(e) ? acc.set(e, true) : acc.set(e, false)
                                return acc
                                }, new Map())

                                return function(hasDup = true) {
                                if(hasDup) return [...mapObj.keys()]
                                else return [...mapObj].filter(([key, val]) => !val).map(([k, v])=> k)
                                }
                                }

                                const getArr = build(arr)

                                console.log(getArr())
                                console.log(getArr(false))








                                share|improve this answer













                                You can use closure and Map






                                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                const build = ar => {
                                const mapObj = ar.reduce((acc, e) => {
                                acc.has(e) ? acc.set(e, true) : acc.set(e, false)
                                return acc
                                }, new Map())

                                return function(hasDup = true) {
                                if(hasDup) return [...mapObj.keys()]
                                else return [...mapObj].filter(([key, val]) => !val).map(([k, v])=> k)
                                }
                                }

                                const getArr = build(arr)

                                console.log(getArr())
                                console.log(getArr(false))








                                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                const build = ar => {
                                const mapObj = ar.reduce((acc, e) => {
                                acc.has(e) ? acc.set(e, true) : acc.set(e, false)
                                return acc
                                }, new Map())

                                return function(hasDup = true) {
                                if(hasDup) return [...mapObj.keys()]
                                else return [...mapObj].filter(([key, val]) => !val).map(([k, v])=> k)
                                }
                                }

                                const getArr = build(arr)

                                console.log(getArr())
                                console.log(getArr(false))





                                let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                const build = ar => {
                                const mapObj = ar.reduce((acc, e) => {
                                acc.has(e) ? acc.set(e, true) : acc.set(e, false)
                                return acc
                                }, new Map())

                                return function(hasDup = true) {
                                if(hasDup) return [...mapObj.keys()]
                                else return [...mapObj].filter(([key, val]) => !val).map(([k, v])=> k)
                                }
                                }

                                const getArr = build(arr)

                                console.log(getArr())
                                console.log(getArr(false))






                                share|improve this answer












                                share|improve this answer



                                share|improve this answer










                                answered 2 days ago









                                birdbird

                                997620




                                997620























                                    4














                                    As many other have said, the first one is just [...new Set(arr)]



                                    For the second, just filter out those that occur more than once:




                                    const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                    const count = (arr, e) => arr.filter(n => n == e).length

                                    const unique = arr => arr.filter(e => count(arr, e) < 2)

                                    console.log(unique(arr));








                                    share|improve this answer




























                                      4














                                      As many other have said, the first one is just [...new Set(arr)]



                                      For the second, just filter out those that occur more than once:




                                      const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                      const count = (arr, e) => arr.filter(n => n == e).length

                                      const unique = arr => arr.filter(e => count(arr, e) < 2)

                                      console.log(unique(arr));








                                      share|improve this answer


























                                        4












                                        4








                                        4







                                        As many other have said, the first one is just [...new Set(arr)]



                                        For the second, just filter out those that occur more than once:




                                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                        const count = (arr, e) => arr.filter(n => n == e).length

                                        const unique = arr => arr.filter(e => count(arr, e) < 2)

                                        console.log(unique(arr));








                                        share|improve this answer













                                        As many other have said, the first one is just [...new Set(arr)]



                                        For the second, just filter out those that occur more than once:




                                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                        const count = (arr, e) => arr.filter(n => n == e).length

                                        const unique = arr => arr.filter(e => count(arr, e) < 2)

                                        console.log(unique(arr));








                                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                        const count = (arr, e) => arr.filter(n => n == e).length

                                        const unique = arr => arr.filter(e => count(arr, e) < 2)

                                        console.log(unique(arr));





                                        const arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];

                                        const count = (arr, e) => arr.filter(n => n == e).length

                                        const unique = arr => arr.filter(e => count(arr, e) < 2)

                                        console.log(unique(arr));






                                        share|improve this answer












                                        share|improve this answer



                                        share|improve this answer










                                        answered 2 days ago









                                        JollyJokerJollyJoker

                                        21115




                                        21115























                                            2

















                                            var arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                                            var map = {};
                                            var finalResult = ;
                                            for (var i = 0; i < arr.length; i++) {
                                            if (!map.hasOwnProperty(arr[i])) {
                                            map[arr[i]] = true;
                                            finalResult.push(arr[i]);
                                            }
                                            }

                                            //if you need it sorted otherwise it will be in order
                                            finalResult.sort(function(a, b) {
                                            return a - b
                                            });

                                            console.log(finalResult);








                                            share|improve this answer






























                                              2

















                                              var arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                                              var map = {};
                                              var finalResult = ;
                                              for (var i = 0; i < arr.length; i++) {
                                              if (!map.hasOwnProperty(arr[i])) {
                                              map[arr[i]] = true;
                                              finalResult.push(arr[i]);
                                              }
                                              }

                                              //if you need it sorted otherwise it will be in order
                                              finalResult.sort(function(a, b) {
                                              return a - b
                                              });

                                              console.log(finalResult);








                                              share|improve this answer




























                                                2












                                                2








                                                2










                                                var arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                                                var map = {};
                                                var finalResult = ;
                                                for (var i = 0; i < arr.length; i++) {
                                                if (!map.hasOwnProperty(arr[i])) {
                                                map[arr[i]] = true;
                                                finalResult.push(arr[i]);
                                                }
                                                }

                                                //if you need it sorted otherwise it will be in order
                                                finalResult.sort(function(a, b) {
                                                return a - b
                                                });

                                                console.log(finalResult);








                                                share|improve this answer


















                                                var arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                                                var map = {};
                                                var finalResult = ;
                                                for (var i = 0; i < arr.length; i++) {
                                                if (!map.hasOwnProperty(arr[i])) {
                                                map[arr[i]] = true;
                                                finalResult.push(arr[i]);
                                                }
                                                }

                                                //if you need it sorted otherwise it will be in order
                                                finalResult.sort(function(a, b) {
                                                return a - b
                                                });

                                                console.log(finalResult);








                                                var arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                                                var map = {};
                                                var finalResult = ;
                                                for (var i = 0; i < arr.length; i++) {
                                                if (!map.hasOwnProperty(arr[i])) {
                                                map[arr[i]] = true;
                                                finalResult.push(arr[i]);
                                                }
                                                }

                                                //if you need it sorted otherwise it will be in order
                                                finalResult.sort(function(a, b) {
                                                return a - b
                                                });

                                                console.log(finalResult);





                                                var arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10];
                                                var map = {};
                                                var finalResult = ;
                                                for (var i = 0; i < arr.length; i++) {
                                                if (!map.hasOwnProperty(arr[i])) {
                                                map[arr[i]] = true;
                                                finalResult.push(arr[i]);
                                                }
                                                }

                                                //if you need it sorted otherwise it will be in order
                                                finalResult.sort(function(a, b) {
                                                return a - b
                                                });

                                                console.log(finalResult);






                                                share|improve this answer














                                                share|improve this answer



                                                share|improve this answer








                                                edited 14 hours ago









                                                demo

                                                2,38433984




                                                2,38433984










                                                answered 2 days ago









                                                JanspeedJanspeed

                                                1,3381315




                                                1,3381315















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