@extra-array/flat/index.js

Flattens nested array to given depth.

'use strict';
function id(v) {
    return v;
}
function is(v) {
    return Array.isArray(v);
}
function flatTo(x, n, fm, ft, a) {
    var i = -1;
    for (var v of x) {
        var v1 = fm(v, ++i, x);
        if (n !== 0 && ft(v1, i, x))
            flatTo(v, n - 1, fm, ft, a);
        else
            a.push(v1);
    }
    return a;
}
function flat(x, n = -1, fm = null, ft = null) {
    var fm = fm || id, ft = ft || is;
    return flatTo(x, n, fm, ft, []);
}
module.exports = flat;