JavaScript var
Example
Create a variable called carName and assign the value "Volvo" to it:
var carName = "Volvo";
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More examples below.
Description
The var statement declares a variable.
Variables are containers for storing information.
Creating a variable in JavaScript is called "declaring" a variable:
var carName;
After the declaration, the variable is empty (it has no value).
To assign a value to the variable, use the equal sign:
carName = "Volvo";
You can also assign a value to the variable when you declare it:
var carName = "Volvo";
Note
A variable declared without a value have the value undefined.
See Also:
JavaScript Reference: JavaScript let
JavaScript Reference: JavaScript const
Tutorials
JavaScript Tutorial: JavaScript Variables
JavaScript Tutorial: JavaScript Let
JavaScript Tutorial: JavaScript Const
JavaScript Tutorial: JavaScript Scope
Syntax
var 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 | Optional. A value to be assigned to the variable. |
Note
ECMAScript6 (ES6 / JavaScript 2015) encourage you to declare variables with let not var.
More Examples
Use var to assign 5 to x and 6 to y, and display x + y:
var x = 5;
var y = 6;
document.getElementById("demo").innerHTML = x + y;
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Use let to assign 5 to x and 6 to y, and display x + y:
let x = 5;
let y = 6;
document.getElementById("demo").innerHTML = x + y;
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Declare many variables in one statement.
Start the statement with var and separate the variables by comma:
var lastName = "Doe",
age = 30,
job = "carpenter";
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Declare many variables in one statement.
Start the statement with let and separate the variables by comma:
let lastName = "Doe",
age = 30,
job = "carpenter";
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Using var in a loop:
let text = "";
for (var i = 0; i < 5; i++) {
text += i + "<br>";
}
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Using let in a loop:
let text = "";
for (let i = 0; i < 5; i++) {
text += i + "<br>";
}
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Browser Support
var is an ECMAScript1 (ES1) feature.
ES1 (JavaScript 1997) is fully supported in all browsers:
| Chrome | Edge | Firefox | Safari | Opera | IE |
| Yes | Yes | Yes | Yes | Yes | Yes |