The static Reflect.has()
method works like the in
operator as a function.
The static Reflect.has()
method works like the in
operator as a function.
Reflect.has(target, propertyKey)
target
The target object in which to look for the property.
propertyKey
The name of the property to check.
A Boolean
indicating whether or not the target
has the property.
The Reflect.has
method allows you to check if a property is in an object. It works like the in
operator as a function.
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
Specification |
---|
ECMAScript Language Specification # sec-reflect.has |
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 |
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/has