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The Symbol.hasInstance well-known symbol is used to determine if a constructor object recognizes an object as its instance. The instanceof operator 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 | ? | ? |