mergeSort.js

function mergeSort(array) {
    if (array.length > 1) {
        let mid = Math.floor(array.length / 2);
        let lhs = mergeSort(array.slice(0, mid));
        let rhs = mergeSort(array.slice(mid));
        return merge(lhs, rhs);
    } else {
        return array;
    }
}

function merge(left, right) {

    let i = 0;
    let j = 0;
    let sortedArr = [];

    while (i < left.length && j < right.length) {
        if (left[i] < right[j]) {
            sortedArr.push(left[i]);
            i++;
        } else {
            sortedArr.push(right[j]);
            j++;
        }
    }
    while (i < left.length) {
        sortedArr.push(left[i]);
        i++;
    }
    while (j < right.length) {
        sortedArr.push(right[j]);
        j++;
    }
    return sortedArr;
}



let myArray = [1, 4, 2, 8, 345, 123, 43, 32, 5643, 63, 123, 43, 2, 55, 1, 234, 92]
console.log(mergeSort(myArray));