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.

Tim Down · Accepted Answer · 2012-09-10 07:31:29Z

17

It is possible in ECMAScript 5 implementations, which include recent versions of all major browsers. The ECMAScript 5 spec adds standardized getters and setters. One quirk is that IE 8 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 also 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.

edited Sep 10, 2012 at 7:31

answered Jul 8, 2010 at 23:39

Tim Down

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1 Comment

shieldgenerator7 Over a year ago

this looks like what I was looking for, but how do you call it when you want to use it in the code?

John Boker · Accepted Answer · 2010-07-08 23:03:55Z

-2

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;

answered Jul 8, 2010 at 23:03

John Boker

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2 Comments

Seattle Leonard Over a year ago

That much I know John. Thank you. I've edited my question. I hope it is a little more clear now.

David Ly Over a year ago

it doesn't seem any clearer to me. Are you looking to add logic to the property getter and setter?

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