var (let / const ) Variable Declaration Statements

Language Reference  Version 1

See Also

Description

Declares a variable.

Syntax

var variable [ = value ] [, variable2 [ = value2], ...]

let variable [ = value ] [, variable2 [ = value2], ...]

const variable [ = value ] [, variable2 [ = value2], ...]

The var, let, const statement syntax has the following parts:

Part	Description
variable, variable2	The names of the variables being declared.
value, value2	The initial value assigned to the variable.

In ES2015 and later, the following have been added to supplement var:

let variable [ = value ] [, variable2 [ = value2], ...]

The let statement also declares and (optionally) assigns a variable, but it will only be available inside the current block of the program. This is a true "local" variable. The advantage is that we can use the same variable name multiple places in the program without them interfering with each other. 1 2

const variable = value [, variable2 = value2, ...]

The const statement declares and (must) assign a constant value. It can not be changed or re-declared, but local variables can be created with the same name via the let statement. By convention, constants are named using all uppercase letters. 1

Remarks

Use the var statement to declare variables. These variables can be assigned values at declaration or later in your script. Examples of declaration follow:

var index;
var name = "Thomas Jefferson";
var answer = 42, counter, numpages = 10;

Also: Basic JavaScript Variables and scope

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