Create javascript property like C# property

Question

Is it possible to create a property on a javascript object that behaves similar to a property in C#.

Example: I've created an auto-sizing textarea widget using dojo. In order to get the "value" property out of my widget, I've hooked up to the onchange event and I'm setting a variable everytime the value of the textarea changes.

Is there a way to accomplish this without hooking up to the onchange event.

Edit

In other words, is it possible to write something in JavaScript that behaves like getters and/or setters.

Answer 1

I'm not sure what you're asking here. You can always get the value of a textarea without the onchange event. you'd have to get the object then look at the value property.

for example, if your textarea has an id="mytext" you can do

var mytextarea = document.getElementById("mytext");
var text = mytextarea.value;

Answer 2

The short answer is no, but there will be in future. The recent ECMAScript 5 spec adds standardized getters and setters, and this will be implemented in browsers in the near future. IE 8 already has this feature, but only on DOM nodes. This is what the syntax looks like:

var obj = {};

Object.defineProperty(obj, "value", {
    get: function () {
        return this.val;
    },
    set: function(val) {
        this.val = val;
    }
});

There has been a proprietary implementation of getters and setters in Mozilla for a long time that was also later adopted by WebKit and Opera but this is not available in IE. The ECMAScript 5 implementation will be adopted by all browsers. Here's an ECMAScript 5 compatibility table that may be of interest: http://kangax.github.com/es5-compat-table/