Dividing an array by filter function

Question

I have a Javascript array that I would like to split into two based on whether a function called on each element returns true or false. Essentially

Answer 1

Try this:

function filter(a, fun) {
    var ret = { good: [], bad: [] };
    for (var i = 0; i < a.length; i++)
        if (fun(a[i])
            ret.good.push(a[i]);
        else
            ret.bad.push(a[i]);
    return ret;
}

DEMO