JavaScript (initial core language support)Baseline · Widely available
JavaScript is a programming language that runs in browsers, usually through the <script> element. JavaScript has changed over many years. This feature represents the oldest language features, such as built-in objects, statements, and operators. Also known as ECMAScript.
Supported in all major browsers for at least 30 months — safe to use without fallbacks. Baseline since Jul 29, 2015. Widely available since Jan 29, 2018.
Browser support
DesktopChrome
1–4Not supported
5+Supportedsince May 25, 2010
Current: 155Edge
12+Supportedsince Jul 29, 2015
Current: 154Firefox
1+Supportedsince Nov 9, 2004
Current: 157Safari
1–4Not supported
5+Supportedsince Jun 7, 2010
Current: 27MobileChrome Android
18+Supportedsince Jun 27, 2012
Current: 155Firefox Android
4+Supportedsince Mar 29, 2011
Current: 157Safari iOS
1–4Not supported
4.2+Supportedsince Nov 22, 2010
Current: 27How to use
This feature is Baseline widely available — use it freely, no fallback needed.
Example
Full syntax and examples are on MDN: Boolean.
Feature detection
JS · check before using
if (typeof Boolean !== "undefined") {
// Boolean is available
}Specification
Sub-features
Support for each part of the feature (102). The overall table above shows when the whole feature works.
| Sub-feature | Chrome | Edge | Firefox | Safari | Chrome Android | Firefox Android | Safari iOS |
|---|---|---|---|---|---|---|---|
| Boolean | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Boolean.Boolean | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Boolean.toString | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Boolean.valueOf | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Error | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Error.Error | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Error.message | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Error.name | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| Error.toString | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| EvalError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| EvalError.EvalError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| RangeError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| RangeError.RangeError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| ReferenceError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| ReferenceError.ReferenceError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| SyntaxError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| SyntaxError.SyntaxError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| TypeError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| TypeError.TypeError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |
| URIError | 1 | 12 | 1 | 1 | 18 | 4 | 1 |