Web/JavaScript/Reference/Global objects/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

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

Browser compatibility

Update compatibility data on GitHub

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

Legend

Full support: Full support
No support: No support