Question

Object.prototype.e = function() {
    [].forEach.call(this, function(e) {
        return e;
    });
}; 
var w = [1,2];

w.e(); // undefined

But this works if I use alert instead

// ...
[].forEach.call(this, function(e) {
    alert(e);
});
// ...

w.e(); // 1, 2

Answer 1

The function e() isn’t returning anything; the inner anonymous function is returning its e value but that return value is being ignored by the caller (the caller being function e() (and can the multiple uses of ‘e’ get any more confusing?))