Question about some wild javascript syntax and contraints

Question

Hey all,

So I know javascript pretty well, but I'm not sure about this one.

Tough to explain so I'll just show it:

var view = new View();

view.rating = 4.5;

Is there anyway to have view.rating be called as a function to manipulate the DOM a bit and set that rating to five?

So in View:

View.prototype = {

  rating : function() {
     $('div.stars').width(4.5);
  }

}

I know there are workarounds, using something other than "view.rating = 5". I'm not interested in those. I'm wondering if there is a way to set this up maintaining view.rating = 5. This is coming JS is coming straight from PHP essentially and I don't want to bog the PHP down with anonymous functions.. like view.rating = function() {...};

Thanks! Matt Mueller

Answer 1

No. (Edit: not on all implementations of common browsers at least)

There isn't anything in Javascript equivalent to "overloading the = operator".

Edit:

I'm not sure if this is clear to you. If you make rating a function (either via the prototype or not), you should call it like view.rating(5), and it can update the DOM (or do anything).

Answer 2

Most implementations of JavaScript don't support creating getter/setter properties so it wouldn't be super useful on the web. However there are some implementations that do. Here's an example in Mozilla's implementation:

• https://developer.mozilla.org/en/Core_JavaScript_1.5_Guide/Creating_New_Objects/Defining_Getters_and_Setters

EDIT: Let me just clarify, writing getters/setters is syntactic sugar over the use of a getFoo()/setFoo(foo) style property. It is for the developer's benefit. IMO, for a web app (due primarily to IE's lack of support) it isn't quite realistic just yet. While IE market share is dropping, depending upon your demographics in a widely public app, a lot of your visitors at this point still won't have support for them.

Some more links of interest for you:

• http://www.robertnyman.com/javascript/#javascript-getters-setters-object-defineproperty-compatibility
• http://ejohn.org/blog/javascript-getters-and-setters/
• http://blogs.msdn.com/ie/archive/2009/01/13/responding-to-change-updated-getter-setter-syntax-in-ie8-rc-1.aspx