Question

I would like to do some stuff after before or after new has run.

function F() {

    this.init = function  () { alert(0) }

}

F.prototype.init = function () { alert(1) }

new F().init(); // Will not run mine, because on new F(), init is reassigned within the class.

I understand I can create my own method function Create() { new F().init() }

But I was wondering if there is a way to hook into the new Function call ?

I hope you understand what I mean.

Answer 1

new is not a function call, F() is. You could do something like this, replacing F with your own delegate.

function F() {
    this.init = function  () { alert(0) }
}

var oldF = F;
F = function() {
    oldF.apply(this, arguments);
    this.init = function() { alert(1); };
};

new F().init();

If you want a utility function to do this kind of thing:

function wrap(constructor, config) {
    return function() {
        constructor.apply(this, arguments);
        for (var key in config) {
            this[key] = config[key];
        }
    }
}

F = wrap(F, {init: function() { alert(1); }});

or use one of many frameworks/libraries (ExtJS, jQuery, Prototype) that provides this stuff.

Following discussion

This can start you off on what you’re trying to do, but I don’t guarantee it works in all situations or implementations (only tested on V8). You could pass the context in which F exists as an additional parameter, or make sure you apply/bind/call extend with it.

function extend(constructor, config) {
    this[constructor.name] = function() {
        constructor.apply(this, arguments);
        for (var key in config) {
            this[key] = config[key];
        }
    }
}

extend(F, {init: function() { alert(1); }});