foo.js

function forEach(array, f) {
    for (i = 0; i < array.length; ++i) {
        f(array[i]);
    }
}

function foo() {
    ret = 4;
    return ret;
}

function map(f, array) {
    ret = [];
    forEach(array, function(element) {
        ret.push(f(element));
    });
    return out;
}