To prototype or not

Details
Written by: Stanko Milosev
Category: JavaScript
Hits: 4756

Consider following example:

var Foo=function () {
	var number = 1;
	self.number = 1;
}

Foo.prototype.bar = function () {
	console.log("test");
};

var foo = new Foo();

foo.bar();

Notice here that in line Foo.prototype.bar = function () I didn't write "var".

This code will work perfectly, in console you will see "test".

Now check following code:

var Foo=function () {
	var number = 1;
	self.number = 1;
	return {inc: function() {
		self.number = self.number + 1;
	}}
}

Foo.prototype.bar = function () {
	console.log("test");
};

var foo = new Foo();

foo.bar();

This code will not work, we will receive error "Uncaught TypeError: undefined is not a function", because with return we will loose "this". Solution is to add return this:

var Foo=function () {
	var number = 1;
	self.number = 1;
	return this;
}

Foo.prototype.bar = function () {
	console.log("test");
};

var foo = new Foo();

foo.bar();