Reflect.has()

Você está lendo a versão em inglês deste conteúdo porque ainda não há uma tradução para este idioma. Ajude-nos a traduzir este artigo!

The static Reflect.has() method works like the in operator as a function.

Syntax

Reflect.has(target, propertyKey)

Parameters

target
The target object in which to look for the property.
propertyKey
The name of the property to check.

Return value

A Boolean indicating whether or not the target has the property.

Exceptions

A TypeError, if target is not an Object.

Description

The Reflect.has method allows you to check if a property is in an object. It works like the in operator as a function.

Examples

Using Reflect.has()

Reflect.has({x: 0}, 'x'); // true
Reflect.has({x: 0}, 'y'); // false

// returns true for properties in the prototype chain 
Reflect.has({x: 0}, 'toString');

// Proxy with .has() handler method
obj = new Proxy({}, {
  has(t, k) { return k.startsWith('door'); }
});
Reflect.has(obj, 'doorbell'); // true
Reflect.has(obj, 'dormitory'); // false

Reflect.has returns true for any inherited properties, like the in operator:

const a = {foo: 123}
const b = {__proto__: a}
const c = {__proto__: b}
// The prototype chain is: c -> b -> a
Reflect.has(c, 'foo') // true

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Reflect.has' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Reflect.has' in that specification.
Draft

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
hasChrome Full support 49Edge Full support 12Firefox Full support 42IE No support NoOpera Full support 36Safari Full support 10WebView Android Full support 49Chrome Android Full support 49Firefox Android Full support 42Opera Android Full support 36Safari iOS Full support 10Samsung Internet Android Full support 5.0nodejs Full support 6.0.0

Legend

Full support  
Full support
No support  
No support

See also