How to create a constant in javascript

Question

I'm designing some classes and for some data I want to use fields that are constant.

Now, AS USUAL, IE does not support the key const so

const T = 10;

not work.

I could create a property via __defineGetter__ and __defineSetter__ to mime that but , AS USUAL, IE does not support that syntax (IE 8 has Object.defineProperty but not work on custom object).

Any idea?

Answer 1

Old question but nowadays you can simply use:

const MY_CONST = 10;

From MDN:

The const declaration creates a read-only reference to a value. It does not mean the value it holds is immutable, just that the variable identifier cannot be reassigned.

Supported by all the main browsers already.

Answer 2

There is a freeze() method in Javascript which can be used to create actual constants.

Usage:

    var consts = {};                    // Object to store all constants
    consts.MY_CONSTANT= 6;
    Object.freeze(consts);              // Make the consts truly read only
    consts.MY_CONSTANT= 7;              // Trying to do this will give error