Are there constants in JavaScript?

Question

Is there a way to use constants in JavaScript?

If not, what\'s the common practice for specifying variables that are used as constants?

Answer 1

An improved version of Burke's answer that lets you do CONFIG.MY_CONST instead of CONFIG.get('MY_CONST').

It requires IE9+ or a real web browser.

var CONFIG = (function() {
    var constants = {
        'MY_CONST': 1,
        'ANOTHER_CONST': 2
    };

    var result = {};
    for (var n in constants)
        if (constants.hasOwnProperty(n))
            Object.defineProperty(result, n, { value: constants[n] });

    return result;
}());

_{* The properties are read-only, only if the initial values are immutable.}