JavaScript Reflect

JavaScript Reflect is a built-in object that gives access to other elements for interceptable operations. This object can be used to check whether an object has a particular property or to change or add new properties to an existing object. This object cannot be explicitly created using the new keyword and we cannot call it a function. Reflect has a set of static functions to perform operations.

Syntax:

Reflect.staticFunc()

Parameters: This object does not have fix parameters, it depends upon the static function being used with it

Return Type: The return values depend on the function being used.

Example 1: This example uses Reflect method to check and add properties in a particular object.

Javascript

var details = {
    name: "Raj",
    course: "DSA",
    website: "geeksforgeeks.org",
}

console.log(Reflect.has(details, "course"))

Reflect.set(details, "Rating", "5");

console.log(details)

Output:

true
{name: 'Raj', course: 'DSA', website: 'geeksforgeeks.org', Rating: '5'}

Example 2: This example uses Reflect functions to construct a new object.

Javascript

class Details {
    constructor(name, course) {
        this.name = name;
        this.course = course;
    }
    get fullDetails() {
        return `${this.name} ${this.course}`;
    }
}

var person = ["Shobhit", "DSA"]

var enroll = Reflect.construct(
    Details,
    person
);

console.log(enroll instanceof Details);
console.log(enroll);

Output:

true
Details {name: 'Shobhit', course: 'DSA'}

Example 3: This example uses Reflect methods to freeze an array so that new elements cannot be added to it.

Javascript

var arr = [];

Reflect.set(arr, 0, "Hello");
Reflect.set(arr, 1, "Welcome");
Reflect.set(arr, 2, "to");
Reflect.set(arr, 3, "GeeksforGeeks");

console.log(arr);
console.log(Reflect.isExtensible(arr))

Reflect.preventExtensions(arr);

Reflect.set(arr, 4, "DSA");

console.log(arr)

Output: Using the preventExtensions method new properties cannot be added to the array. This helps to freeze the array

(4) ['Hello', 'Welcome', 'to', 'GeeksforGeeks']
true
(4) ['Hello', 'Welcome', 'to', 'GeeksforGeeks']

Supported Browsers:

• Chrome
• Edge
• Firefox
• Opera
• Safari

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