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

"use strict";

var constants = Object.freeze({
    "π": 3.141592653589793 ,
    "e": 2.718281828459045 ,
    "i": Math.sqrt(-1)
});

constants.π;        // -> 3.141592653589793
constants.π = 3;    // -> TypeError: Cannot assign to read only property 'π' …
constants.π;        // -> 3.141592653589793

delete constants.π; // -> TypeError: Unable to delete property.
constants.π;        // -> 3.141592653589793

See Object.freeze. You can use const if you want to make the constants reference read-only as well.