Hook Javascript Class Function

ClassHooker.js

/**
 * ClassHooker
 * Hook original JavaScript class.
 */
var origionalClass = function (z, y) {
	console.group('Debug: origionalClass');
	console.log ('arguments:');
	console.log (arguments);

	this.arg1 = z;
	this.arg2 = y;
	this.end = function () {
		console.log ('== this.end called.');
		console.log ('this:');
		console.log (this);
		console.groupEnd ();
	};
};

var ClassProxy = function (that, target) {
	for (var i=2, args=[that || {}]; i<arguments.length; i++)
		args.push (arguments[i]);

	var r = new (Function.prototype.bind.apply (target, args));

	// Modify original class.
	r.jixun = true;
	return r;
};

var modifiedClass = new ClassProxy ({}, origionalClass, 123, 345);
modifiedClass.end ();

// To make this re-usable, I created this handy function.
// Again with original Class, but with callback this time.
var classHook = function (target, callback, that) {
	// Bind init. arguments.
	for (var i=3, args=[that || {}]; i<arguments.length; i++)
		args.push (arguments[i]);

	return (function () {
		for (var i = 0, eArgs = args.slice(); i < arguments.length; i++)
			eArgs.push (arguments[i]);

		// When this is initialised, callback.
		var r = new (Function.prototype.bind.apply (target, eArgs));

		// If nothing returned, use the original data instead.
		return callback (r, eArgs) || r;
	});
};

// Replace old class content with hooked class content.
origionalClass = classHook (origionalClass, function (r, eArgs) {
	// Modify class attribute.
	r.jixun = eArgs[3];
});

// `this` have independent scope and is fixed.
var callToOrigionalClass1 = new origionalClass (1, 2, 233);
var callToOrigionalClass2 = new origionalClass (1, 2, 234);
callToOrigionalClass2.end ();
callToOrigionalClass1.end ();

null;