Added a brief and simple JavaScript OOP rundown...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>

js-oop.js

@@ -0,0 +1,130 @@
+/**********************************************************************
+* 
+* The basics of JavaScript OOP
+*
+*
+**********************************************************************/
+//
+// The value of 'this'
+// -------------------
+//
+ 	function f(){
+ 		console.log(this)
+ 		this.a = 1
+ 	}
+	var o = { f: f }
+
+// 
+// 'this' is always the "context" of the function call, in JS a context
+// can be:
+// 	- implicit
+// 		- root context
+ 			f()			// 'window' or 'module' is implied, this is 
+ 						//	equivalent to: window.f()
+// 		- 'new' context
+ 			new f()		// here a context will be created and passed to
+ 						//	'f's 'this', for more details on what 'new'
+ 						//	does see the next section.
+// 	- explicit:
+// 		- the object on the left side of "." or the [ ] attribute access:
+ 			o.f()		// o is the context
+ 			o['f']()	// the same as the above
+// 		- the object explicitly passed to .call(..) or .apply(..) methods
+// 		  as first argument:
+ 		  	f.call(o)	// o is the context
+//
+//
+//
+// What's 'new'?
+// -------------
+//
+ 	function O(){
+ 		this.attr = 123
+ 	}
+ 	var o = new O()
+
+//
+// 'new' creates a new context object and passes it to the function 
+// being called (the constructor), this new object has several special
+// attributes set:
+// 	o.constructor	-- references the object (constructor) used to 
+// 						construct the object o (instance)
+// 	o.__proto__		-- references the constructor prototype, same as:
+ 							o.constructor.prototype === o.__proto__
+// 						this is used to identify the object via:
+ 							o instanceof O
+//
+// The 'new' expression returns the context object after it has been
+// populated by the constructor function.
+//
+// NOTE: when using 'new', the function return value is ignored.
+//
+//
+// The values set on 'this' by the constructor are instance attributes,
+// i.e. they are stored in the specific instance being created.
+//
+// NOTE: calling the constructor is not required, but not calling it
+// 		will not run the initialization code that would otherwise 
+// 		populate the object. i.e. no instance values will be created.
+// 
+//
+// The instance has another type of attribute accessible through it that
+// is not stored in it, but rather in it's prototype (o.__proto__), or 
+// rather the constructor's prototype (o.constructor.prototype). For 
+// more details see the next section.
+//
+//
+//
+// The object's 'prototype'
+// ------------------------
+//
+ 	function f(){}
+ 	console.log(f.prototype)			// f {}
+
+//
+// The unique prototype object is created on every function definition.
+// The prototype is instance-like of the function to which it is assigned.
+//
+// NOTE: since the prototype has .__proto__ set to Object, technically
+// 		it's not a strict instance of the type it defines, so:
+ 			f.prototype instanceof f
+// 		will return false.
+//
+// Each unresolved attribute access on the "instance" will resolve to its
+// prototype (o.__proto__ or o.constructor.prototype). 
+//
+ 	O.prototype.x = 321
+ 	console.log(o.x)					// 321
+
+//
+// Since the prototype is a JS object that adheres to the same rules as 
+// any other object, if the attr is not resolved in it directly it will 
+// be searched in its prototype, and so on.
+// This principle enables us to implement inheritance.
+//
+	var OO = function(){
+		// call the base constructor...
+		O.call(this)
+	}
+	// chain the two prototypes...
+	OO.prototype = new O()
+	// this is to make things coherent for oo below...
+	OO.prototype.constructor = OO
+
+	var oo = new OO()
+
+	console.log(oo.x)					// 321
+	console.log(oo.constructor.name)	// 'OO'
+
+//
+// So in the example above local attributes (in 'oo') will be searched 
+// first, then oo.__proto__ (instance of O), then in O.prototype, and 
+// then in Object.prototype.
+//
+// 	oo -> oo.__proto__ -> (oo.__proto__).__proto__ -> ...
+//
+//
+//
+// 				
+/**********************************************************************
+* vim:set ts=4 sw=4 :                                                */