Hidden Features of MooTools

Question

What are the hidden or obscure features of MooTools that every MooTools developer should be aware of?

One feature per answer, please.

Answer 1

Class Mutators

MooTools has a wonderful feature that allows you to create your own Class mutators. Eg, to add a logger for particular class methods being referenced, you can do:

// define the mutator as 'Monitor', use as Mointor: ['methodname', 'method2'...]
Class.Mutators.Monitor = function(methods){
    if (!this.prototype.initialize) this.implement('initialize', function(){});
    return Array.from(methods).concat(this.prototype.Monitor || []);
};

Class.Mutators.initialize = function(initialize){
    return function(){
        Array.from(this.Monitor).each(function(name){
           var original = this[name];
           if (original) this[name] = function() {
               console.log("[LOG] " + name, "[SCOPE]:", this, "[ARGS]", arguments);
               original.apply(this, arguments);
           }
        }, this);
        return initialize.apply(this, arguments);
    };
};

and then in the Class:

var foo = new Class({

    Monitor: 'bar',

    initialize: function() {
        this.bar("mootools");
    },

    bar: function(what) {
        alert(what);
    }

});

var f = new foo();
f.bar.call({hi:"there from a custom scope"}, "scope 2");

Try the jsfiddle: http://jsfiddle.net/BMsZ7/2/

This little gem has been instrumental to me catching nested bugfoot race condition issues inside a HUUUGE async webapp that would have been so difficult to trace otherwise.

Answer 2

Function.prototype.protect is maybe a lesser known nice one.

Is used to have protected methods in classes:

var Foo = new Class({

    fooify: function(){
        console.log('can\'t touch me');
    }.protect(),

    barify: function(){
        this.fooify();
    }

});

 var foo = new Foo();
 foo.fooify(); // throws error
 foo.barify(); // logs "can't touch me"

Personally I don't use it very often, but it might be useful in some cases.