gistfile1.txt

var a = [];

function generateRandomData(limit) {
    const alphabet = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"];
    for (let i = 0; i < limit; i++) {
        let item = alphabet[Math.floor(Math.random() * alphabet.length)];
        a.push(item);
    }
}
generateRandomData(10000);

function split() {
    for (let increment = 1; increment <= a.length; increment *= 2) {
        for (let initial = 0; initial < a.length; initial += increment * 2) {
            let left = a.slice(initial, (initial + increment));
            let right = a.slice((initial + increment), (initial + increment + increment))
            compare(left, right, initial);
        }
    }
    console.log(a);
}

function compare(left, right, pos) {
    let leftIndex = 0;
    let rightIndex = 0;
    let result = [];
    while (result.length < (left.length + right.length)) {
        if (left[leftIndex] <= right[rightIndex] || right[rightIndex] === undefined) {
            result.push(left[leftIndex]);
            leftIndex++;
        } else {
            result.push(right[rightIndex]);
            rightIndex++;
        }
    }

    let newLeft = a.slice(0, pos);
    let newRight = a.slice((result.length + pos), a.length);
    a = newLeft.concat(result, newRight);
}

split();