The Symbol.hasInstance
well-known symbol is used to determine if a constructor object recognizes an object as its instance. The instanceof
operator's behavior can be customized by this symbol.
Property attributes of Symbol.hasInstance |
|
---|---|
Writable | no |
Enumerable | no |
Configurable | no |
Examples
You could implement your custom instanceof
behavior like this, for example:
class MyArray { static [Symbol.hasInstance](instance) { return Array.isArray(instance); } } console.log([] instanceof MyArray); // true
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Symbol.hasInstance' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of 'Symbol.hasInstance' in that specification. |
Living Standard |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 51 | Yes | 50 | No | Yes | Yes |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | 50 | No | Yes | Yes |