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const input = ['one', 'two', 'three', 'four'];

const last = input.pop();

const result = input.join(', ') + ' and ' + last;

console.log(result);

function makeString(arr) {

  if (arr.length === 1) return arr[0];

  const firsts = arr.slice(0, arr.length - 1);

  const last = arr[arr.length - 1];

  return firsts.join(', ') + ' and ' + last;

}



console.log(makeString(['one', 'two', 'three', 'four']));

console.log(makeString(['one']));

function makeCommaSeparatedString(arr, useOxfordComma) {

    const listStart = arr.slice(0, -1).join(', ');

    const listEnd = arr.slice(-1);

    const conjunction = arr.length <= 1 ? '' :

        useOxfordComma && arr.length > 2 ? ', and ' : ' and ';



    return [listStart, listEnd].join(conjunction);

}



console.log(makeCommaSeparatedString(['one', 'two', 'three', 'four']));

// one, two, three and four

console.log(makeCommaSeparatedString(['one', 'two', 'three', 'four'], true));

// one, two, three, and four

console.log(makeCommaSeparatedString(['one', 'two'], true));

// one and two

console.log(makeCommaSeparatedString(['one']));

// one

console.log(makeCommaSeparatedString());

// 

const lf = new Intl.ListFormat('en');

lf.format(['Frank']);

// → 'Frank'

lf.format(['Frank', 'Christine']);

// → 'Frank and Christine'

lf.format(['Frank', 'Christine', 'Flora']);

// → 'Frank, Christine, and Flora'

lf.format(['Frank', 'Christine', 'Flora', 'Harrison']);

// → 'Frank, Christine, Flora, and Harrison'

const input1 = ['one', 'two', 'three', 'four'];

const input2 = ['A Tale of Two Cities', 'Harry Potter and the smth', 'One Fish, Two Fish, Red Fish, Blue Fish'];

const input3 = ['one', 'two'];

const input4 = ['one'];

const input5 = ;



const result = a => a.length > 1 

  ? `${a.slice(0, -1).join(', ')} and ${a.slice(-1)}` 

  : {0: '', 1: a[0]}[a.length];



console.log(result(input1));

console.log(result(input2));

console.log(result(input3));

console.log(result(input4));

console.log(result(input5));

let arrayToCustomStr = (arr, enableMutate) =>

{

    // Clone the received array (if required).

    let a = enableMutate ? arr : arr.slice(0);



    // Convert the array to custom string.

    let removed = a.splice(-2, 2);

    a.push(removed.join(" and "));

    return a.join(", ");

}



// First example, mutate of original array is disabled.

let input1 = ['one', 'two', 'three', 'four'];

console.log("Result for input1:" , arrayToCustomStr(input1));

console.log("Original input1:", input1);



// Second example, mutate of original array is enabled.

let input2 = ['one', 'two'];

console.log("Result for input2:", arrayToCustomStr(input2, true));

console.log("Original input2:", input2);



// Third example, lenght of array is 1.

let input3 = ['one'];

console.log("Result for input3:", arrayToCustomStr(input3));



// Fourth example, empty array.

let input4 = ;

console.log("Result for input4:", arrayToCustomStr(input4));



// Plus example.

let bob = [

    "Don't worry about a thing",

    "Cause every little thing",

    "Gonna be all right",

    "Saying, don't worry about a thing..."

];

console.log("Result for bob:", arrayToCustomStr(bob));

.as-console-wrapper {

    top: 0px;

    max-height: 100% !important;

}