Get combinations of all elements in an array with optional length filter.

get-combinations.js

//Based on https://stackoverflow.com/a/42531964

function combinations(array, length) {
    const arr = new Array(1 << array.length).fill().map(
        (e1, i) => array.filter((e2, j) => i & 1 << j));
    return length ? arr.filter(a => a.length == length) : arr;
}

//console.log(combinations([1, 2, 3, 8, 10], 2));