Defining read-only properties in JavaScript

Question

Given an object obj, I would like to define a read-only property 'prop' and set its value to val. Is this the proper way to do that?

Object.defineProperty( obj, 'prop', {
    get: function () {
        return val;
    }
});

The result should be (for val = 'test'):

obj.prop; // 'test'
obj.prop = 'changed';
obj.prop; // still 'test' since it's read-only

This method works btw: http://jsfiddle.net/GHMjN/
I'm just unsure if this is the easiest / smoothest / most proper way to do it...

Answer 1

You could instead use the writable property of the property descriptor, which prevents the need for a get accessor:

var obj = {};
Object.defineProperty(obj, "prop", {
    value: "test",
    writable: false
});

As mentioned in the comments, the writable option defaults to false so you can omit it in this case:

Object.defineProperty(obj, "prop", {
    value: "test"
});

This is ECMAScript 5 so won't work in older browsers.