Returns the permutations of the array A

permutations.js

let permutations = A => {
    let N = A.length;
    let perms = [];
    let go = (i = 0) => {
        if (i == N) {
            perms.push([...A]);
            return;
        }
        for (let k = i; k < N; ++k) {
            [A[i], A[k]] = [A[k], A[i]];
            go(i + 1);
            [A[i], A[k]] = [A[k], A[i]];
        }
    };
    go();
    return perms;
};