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CSSStyleDeclaration JS Conversion


JavaScript const

Constant Array:

// Create an array:
const cars = ["Saab", "Volvo", "BMW"];

// Change an element:
cars[0] = "Toyota";

// Add an element:
cars.push("Audi");
Try it Yourself »

Constant Object:

// Create an object:
const car = {type:"Fiat", model:"500", color:"white"};

// Change a property:
car.color = "red";

// Add a property:
car.owner = "Johnson";
Try it Yourself »

Definition and Usage

The const statement declares a variable.

Variables are containers for storing information.

Creating a variable in JavaScript is called "declaring" a variable:

const name = "Volvo";

Note

A const variable must be assigned when it is declared.

See Also:

JavaScript Reference: JavaScript var

JavaScript Reference: JavaScript let

Tutorials:

JavaScript Tutorial: JavaScript Variables

JavaScript Tutorial: JavaScript const

JavaScript Tutorial: JavaScript let

JavaScript Tutorial: JavaScript Scope


Syntax

const name = value;

Parameters

Parameter Description
name Required.
The name of the variable.
Variable names must follow these rules:

Must begin with a letter, or $, or _
Names are case sensitive (y and Y are different)
Reserved JavaScript words cannot be used as names
value Required.
A value to be assigned to the variable.


When to use JavaScript const?

As a general rule, always declare a variable with const unless you know that the value will change.

Use const when you declare:

  • A new Array
  • A new Object
  • A new Function
  • A new RegExp

Browser Support

const is supported in all modern browsers:

Chrome IE Edge Firefox Safari Opera
Yes 11 Yes Yes Yes Yes

const is an ECMAScript6 (ES6 - JavaScript 2015) feature.