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. 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()

var 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


Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Reflect.defineProperty' in that specification.
Standard Initial definition.
ECMAScript 2017 Draft (ECMA-262)
The definition of 'Reflect.defineProperty' in that specification.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 49 42 (42) No support No support No support
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support 42.0 (42) No support No support No support

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

ECMAScript6 JavaScript Method Reflect