All permutations

permutations.js

function* allPermutations(arr) {
    const c = new Array(arr.length).fill(0);
    let i = 1;
    while (i < arr.length) {
        if (c[i] < i) {
            yield [...arr];
            const k = i % 2 && c[i];
            [arr[i], arr[k]] = [arr[k], arr[i]]; 
            ++c[i];
            i = 1;
        }
        else {
            c[i] = 0;
            ++i;
        }
    }
}