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Reflect.defineProperty

The static Reflect.defineProperty() method is like Object.defineProperty() but returns a Boolean.

Syntax

Reflect.defineProperty(target, propertyKey, attributes)

Parameters

target
The target object on which to define the property.
propertyKey
The name of the property to be defined or modified.
attributes
The attributes for the property being defined or modified.

Return value

A Boolean indicating whether or not the property was successfully defined.

Exceptions

A TypeError, if target is not an Object.

Description

The Reflect.defineProperty method allows precise addition to or modification of a property on an object. For more details, see the Object.defineProperty which is similar.

One key difference: Object.defineProperty returns the object or throws a TypeError if the property has not been successfully defined. Reflect.defineProperty, however, simply returns a Boolean indicating whether or not the property was successfully defined.

Examples

Using Reflect.defineProperty()

let obj = {}
Reflect.defineProperty(obj, 'x', {value: 7})  // true
obj.x                                         // 7

Checking if property definition has been successful

With Object.defineProperty, which returns an object if successful, or throws a TypeError otherwise, you would use a try...catch block to catch any error that occurred while defining a property.

Because Reflect.defineProperty returns a Boolean success status, you can just use an if...else block here:

if (Reflect.defineProperty(target, property, attributes)) {
  // success
} else {
  // failure
}

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
defineProperty 49 12 42 No 36 10
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
defineProperty 49 49 42 36 10 5.0
Server
Node.js
defineProperty 6.0.0

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/defineProperty