Symbol.hasInstance

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 2017 Draft (ECMA-262)
The definition of 'Symbol.hasInstance' in that specification.
Draft  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 51 50 (50) No support ? ?
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? ? 50.0 (50) No support ? ?

See also

Document Tags and Contributors

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