W3cubDocs

/JavaScript

Reflect.has()

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

Try it

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

Browser compatibility

Desktop Mobile Server
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet Deno Node.js
has
49
12
42
No
36
10
49
49
42
36
10
5.0
1.0
6.0.0

See also

© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/has