The biggest reason not to use the 2nd form is that you’ll end up eliminating anything else that existed in the prototype before you assign it. If that isn’t something you’re concerned with there’s no reason not to declare it the way you’ve demonstrated.
Well, if you want to make B.prototype an object that inherits from A.prototype, without executing the A constructor, to avoid all possible side-effects, you could use a dummy constructor to do it, for example: function tmp() {} tmp.prototype = A.prototype; B.prototype = new tmp(); B.prototype.constructor = B; You could create a function to encapsulate the … Read more
The prototype system offers a captivating model of metaprogramming, by implementing inheritance via standard objects. Of course, this is mostly used to express the established and simple concept of classes of instances, but without classes as language-level immutable structures that need specific syntax to create them. By using plain objects, all you can do to … Read more
The answer to the real question is that you need to do both: Setting the prototype to an instance of the parent initializes the prototype chain (inheritance), this is done only once (since the prototype object is shared). Calling the parent’s constructor initializes the object itself, this is done with every instantiation (you can pass … Read more
For preserving the context, the bind method is really useful, it’s now part of the recently released ECMAScript 5th Edition Specification, the implementation of this function is simple (only 8 lines long): // The .bind method from Prototype.js if (!Function.prototype.bind) { // check if native implementation available Function.prototype.bind = function(){ var fn = this, args … Read more
To add to Norbert Hartl’s answer, SuperCar.prototype.constructor isn’t needed, but some people use it as a convenient way of getting the constructing function of an object (SuperCar objects in this case). Just from the first example, Car.call(this, name) is in the SuperCar constructor function because when you do this: var mySuperCar = new SuperCar(“SuperCar”); This … Read more
I’ve been trying to wrap my head around this recently and finally came up with this “map” that I think sheds full light over the matter http://i.stack.imgur.com/KFzI3.png I know I’m not the first one making this up but it was more interesting figuring it out that finding it :-). Anyway, after that I found e.g. … Read more
There are about a hundred terminology issues here, mostly built around someone (not you) trying to make their idea sound like The Best. All object oriented languages need to be able to deal with several concepts: encapsulation of data along with associated operations on the data, variously known as data members and member functions, or … Read more
Using the prototype makes faster object creation since properties/methods on the prototype don’t have to be re-created each time a new object is created. When you do this: function animal() { this.name=”rover” this.set_name = function (name) { this.name = name } } The set_name method is created every time you create an animal. But when … Read more