JavaScript let
Example
Create a variable called carName and assign the value "Volvo" to it:
let carName = "Volvo";
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More examples below.
Description
The let statement declares a variable.
Variables are containers for storing information.
Creating a variable in JavaScript is called "declaring" a variable:
let 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:
let carName = "Volvo";
Note
A variable declared without a value have the value undefined.
See Also:
JavaScript Reference: JavaScript var
JavaScript Reference: JavaScript const
Tutorials:
JavaScript Tutorial: JavaScript Variables
JavaScript Tutorial: JavaScript let
JavaScript Tutorial: JavaScript const
JavaScript Tutorial: JavaScript Scope
Syntax
let 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. |
More Examples
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 let and separate the variables by comma:
let lastName = "Doe",
age = 30,
job = "carpenter";
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Use let in a loop:
let text = "";
for (let i = 0; i < 5; i++) {
text += i + "<br>";
}
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Browser Support
let is an ECMAScript6 (ES6) feature.
ES6 (JavaScript 2015) is supported in all modern browsers since June 2017:
| Chrome 51 | Edge 15 | Firefox 54 | Safari 10 | Opera 38 |
| May 2016 | Apr 2017 | Jun 2017 | Sep 2016 | Jun 2016 |
let is not supported in Internet Explorer.