Split up an array into groups of n values.

partitionArray.js

function partitionArray(arr, n) {

    const res = [];

    for (let i = 0; i < Math.floor(arr.length / n); i++) {

        res.push(arr.slice(i * n, (i + 1) * n));

    }

    res.push(arr.slice(Math.floor(arr.length / n) * n));

    return res;

}