I searched if JavaScript offers a mean to define symbolic constants, but didn't find anything. Did I miss something ?

Is it a mon practices to use const var instead ?

var const MAXIMUM_VALUE = 100; 

Thanx.

I searched if JavaScript offers a mean to define symbolic constants, but didn't find anything. Did I miss something ?

Is it a mon practices to use const var instead ?

var const MAXIMUM_VALUE = 100; 

Thanx.

• javascript
• constants

3 Answers 3

const is not supported by IE, so if you want to support IE that is out of the question.

As far as I know, and the best way of doing this to keep it simple is to just have a naming convention for your constants like the ever-popular ALL UPPERCASE. There are some examples out there to force constants but they are not worth it for the most part. Alternatively, you could use a function:

function myConst() { return 'myValue'; }

This can of course still be overridden but I've seen it used.

Also see:

• Are there constants in Javascript?
• Is it possible to simulate constants in Javascript using closures?
• Javascript: final / immutable global variables?

Yes. But you remove the var. const replaces var.

const MAXIMUM_VALUE = 100;

Object.defineProperty(window, 'CONSTANT_NAME', {value: CONSTANT_VALUE});

// usage
console.log(CONSTANT_NAME);

Object.defineProperty() creates a property with the following default attributes:

• configurable true if and only if the type of this property descriptor may be changed and if the property may be deleted from the corresponding object. Defaults to false.

• enumerable true if and only if this property shows up during enumeration of the properties on the corresponding object. Defaults to false.

• writable true if and only if the value associated with the property may be changed with an assignment operator. Defaults to false.

if the "constant" is an object you might additionally want to make it immutable by freezing it. obj =Object.freeze(obj). have in mind that child-property-objects are not automatically frozen.