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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support51 Yes50 No Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes50 No Yes Yes

See also

Document Tags and Contributors

 Contributors to this page: fscholz, jameshkramer, kdex, GoToLoop, ZeikJT
 Last updated by: fscholz,