Javascript Merge Sort

merge-sort.js

// For each side of a set of arrays
const mergeArrays = (left, right) => {

    // Iterate each 0th value moving the vaues into our sorted array
    let sortVals = [];
    while(left.length && right.length) {
        (left[0] < right[0]) ? sortVals.push(left.shift()) : sortVals.push(right.shift());
    }

    // Return sorted array & anything leftover from either side
    return [...sortVals, ...left, ...right];
};

// A recursive function which will return a sorted array
const mergeSort = array => {

    // Base case
    if(array.length === 1) {
        return array;
    }

    // Split our array
    let left = [];
    const midPoint = array.length / 2;
    while (left.length < parseInt(midPoint)) {
        left.push(array.shift());
    }

    // Recursively split & merge (sort) our arrays
    return mergeArrays(mergeSort(left), mergeSort(array));
};

// Usage

// First Get an array of randomish numbers :p
var array = [];

for(var i = 0; i < 100000; i++) {
    let newVal = 0;
    while(newVal < 1) {
        let valA = Math.random() * 9;
        let valB = Math.random() * 14;
        let rand = Math.random() * 10;
        newVal = parseInt((valA + valB) / rand);
    }
    array.push(newVal);
}

// Call the recursive function with your array
console.log(mergeSort(array));