Object.prototype.toString enables really fucking cool equality comparison...

gistfile1.js

// Comparison in JavaScript is an interesting thing...

var Object1 = {
	toString: function() { return "!!!"; }
};

var Object2 = {
	toString: function() { return "!!!"; }
};

var MySuperRadFunky = Class.create({
	initialize: function( ) {
		// Do some crazy shit here
	},
	toString: function() { return "!!!"; }
});

RegExp.prototype.toString = function() {
	return "!!!";
};

console.log("!!!" == Object1); // true
console.log("!!!" === Object1); // false

console.log("!!!" == Object2); // true
console.log("!!!" === Object2); // false

console.log("!!!" == new MySuperRadFunky()); // true
console.log("!!!" === new MySuperRadFunky()); // false

console.log("!!!" == new RegExp("")); // true
console.log("!!!" === new RegExp("")); // false


// Example use-case for smart toString methods which enable comparison

/**
 *  class ThingCollection
 **/
var ThingCollection = Class.create({
	initialize: function() { this._collection = []; },
	add: function(value) { this._collection.push(value); return this; },
	
	/**
	 *  Custom toString implementation returns the size of the collection
	 *  enabling comparison by number using the == operator, ie: myCollection == 5
	 **/
	toString: function() { return this._collection.length.toString(); }
});

var myCollection = new ThingCollection();
console.log(5 == myCollection); // false

myCollection.add(null).add("something");
console.log(5 == myCollection); // false

myCollection.add("rad").add("awesome").add("stuff");
console.log(5 == myCollection); // true!!!
// myCollection is getting converted to "5" automatically via the ThingCollection.toString method
// And since myCollection is converted to the String "5", 5 is also converted to a string
// before comparison.