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


Reflect.defineProperty(target, propertyKey, attributes)


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

Return value

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


A TypeError, if target is not an Object.


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.


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


ECMAScript (ECMA-262)
The definition of 'Reflect.defineProperty' in that specification.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
definePropertyChrome 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


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See also