Question

Trying to grasp Prototyping in Javascript. Trying to create my own namespace to extend the String object in JavaScript.

Here is what I have so far (a snippet):

var ns {
 alert: function() {
  alert (this);
 }
}
String.prototype.$ns = ns;

As you can see, I am trying to place what will be a series of functions into the ns namespace. So I can execute a command like this:

"hello world".$ns.alert();

But the problem is, the this doesn’t reference the text being sent (in this case, “hello world”). What I get is an alert box with the following:

[object Object]

Not having a full grasp of the object-oriented nature of JavaScript, I am at a loss, but I am guessing I am missing something simple.

Does anyone know how to achieve this (get the source text from the nested object)? Short of that, I am left with having to do procedural programming ( ns.alert(“hello world”); ) which I am trying to avoid.

Thanks –

Answer 1

This is happening because when you invoke a reference, its base object is set as the this value of the invoked method (more technical details here).

So when you invoke "hello world".$ns.alert(); the this value inside your alert method, will refer to "hello world".$ns, which is String.prototype.$ns.

I don’t think adding object levels (namespaces) inside the prototype of built-in objects can be useful, I usually recommend to not modify objects you don’t own.