I think it’s particularly helpful if you are using a Javascript library because many of them use prototypes to simulate classic inheritance and if things go wrong it’s really hard to debug without understanding what’s going on.

That said.. I should update my article with a more convincing argument in the object prototype’s favour. :)

The Pet.prototype.sayHello example is simplistic to illustrate the idea. In the real world, javascript classes are much more significant in size, and can have rather large methods. If I have 1000 instances of an object, without prototype I would have 1000 instances of that large method as well. With prototype, the sayHello method will be included but only as a reference to the single existing method, which translates to a significant reduction in memory usage.
I’m all for simplified programming, but would have to defend prototype as a necessity.

I also wonder if using Pet.prototype.sayHello= does actually save memory. I tested the rufus object on my system and it still included the sayHello method even if Pet.prototype.sayHello= was used.

String.prototype.trim = function()
{
alert(“this function can trim a string object”);
}
var moo = “Hello world”;
moo.trim();

In Firefox, Safari, Chrome and Opera you can also extend HTML elements:

window.onload = function()
{
HTMLElement.prototype.moo = function()
{
alert(“Calling the HTML Element’s moo function”);
}
document.body.moo();
}

In IE (I just tested in IE8) you can’t extend the DOM objects because they’re not part of javascript, they’re really COM objects.

You can see the full example here: http://helephant.com/wp-content/uploads/2009/01/built-in-prototype.html

Anyway, thought you might like to enhance your comment fields with tabs. Makes it easier for us coders to indent our code when we’re discussing.

http://teddevito.com/demos/textarea.html