Merge Sort Algorithm Example

mergeSort.js

function merge(firstArray, secondArray) {

    let results = [], firstArrayIndex = 0, secondArrayIndex = 0;

    while (firstArrayIndex < firstArray.length && secondArrayIndex < secondArray.length) {

        if (secondArray[secondArrayIndex] > firstArray[firstArrayIndex]) {
            results.push(firstArray[firstArrayIndex])
            firstArrayIndex++;
        } else {
            results.push(secondArray[secondArrayIndex])
            secondArrayIndex++;
        }
    }

    while (firstArrayIndex < firstArray.length) {
        results.push(firstArray[firstArrayIndex]);
        firstArrayIndex++;
    }

    while (secondArrayIndex < secondArray.length) {
        results.push(secondArray[secondArrayIndex]);
        secondArrayIndex++;
    }

    return results;
}


function mergeSort(arr) {

    if (arr.length <= 1) return arr;

    let mid = Math.floor(arr.length / 2);
    let left = mergeSort(arr.slice(0, mid));
    let right = mergeSort(arr.slice(mid));

    return merge(left, right);
}

const numberList = [...new Set(Array.from({ length: 50 }, () => Math.floor(Math.random() * 250)))];
console.log(mergeSort(numberList))