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. 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()

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
}

Specifications

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.	Draft

Browser compatibility

See also

• Reflect
• Object.defineProperty()