JavaScript Reflect defineProperty() Method

JavaScript Reflect.defineProperty() method in JavaScript is used to allow the precise addition to or modification of a property on an object. This method returns a Boolean value which indicates whether the property was successfully defined.

Syntax:

Reflect.defineProperty(target, propertyKey, attributes) 

Parameter: This method accepts three parameters as mentioned above and described below:

• target: This parameter defines the property and the target object.
• propertyKey: This parameter is the name of the property which is to be defined or modified.
• Attributes: This parameter is the attributes for the property which is being defined or modified.

Return value: This method returns a Boolean value which indicates whether the property was successfully defined.

Exceptions: A TypeError is an exception given as the result when the target is not an Object.

Below examples illustrate the Reflect.defineProperty() method in JavaScript:

Example 1: The below example shows the basic use of the Reflect.defineProperty() method in JavaScript.

javascript

<script>
    const object1 = {};

    if (Reflect.defineProperty(object1, 'geeks1', {value: 42})) {
      console.log('geeks1 assigned');

    } else {
      console.log('problem created by  geeks1');
    }

    console.log(object1.geeks1);

    const object2 = {};
    const object3 = {};
    (Reflect.defineProperty(object2, 'geeks2', {value: 97}))
    if (Reflect.defineProperty(object3, 'geeks3', {value: 23})) {
      console.log('geeks3 assigned');
    } else {
      console.log('problem created by geeks3');
    }
    console.log(object3.geeks3);
    console.log(object2.geeks2);
</script>

Output:

"geeks1 assigned"
42
"geeks3 assigned"
23
97

Example 2: The below example shows the basic use of the Reflect.defineProperty() method in JavaScript.

javascript

<script>
    const a = {};
    const result = Reflect.defineProperty(a, "geek1",
    { value : 19, });

    console.log(a);
    console.log( result);

    const b = {};
    const result1 = Reflect.defineProperty(b, "geek2",
    { value : 56,
      writable: false
    }
    );
    console.log(b );
    console.log(result1);

    let obj = {}
    Reflect.defineProperty(obj, 'x', {value: 71})  // true
    console.log(obj.x)
</script>

Output:

Object {  }
true
Object {  }
true
71

Supported Browsers: The browsers are supported by JavaScript Reflect.defineProperty() Method are listed below:

• Google Chrome 49 and above
• Edge 12 and above
• Firefox 42 and above
• Opera 36 and above
• Safari 10 and above

We have a complete list of Javascript Reflects methods, to check those go through the JavaScript Reflect Reference article.