JavaScript Object Prototypes

JavaScript prototypes are used to access the properties and methods of objects. Inherited properties are originally defined in the prototype or parent object. The Date object is inherited from Date.prototype, Array object inherits from Array.prototype, etc. The prototypes may be used to add new properties and methods to the existing objects and object constructor.

Syntax:

Object.prototype

Example 1: This example adds a new property to the object.

Javascript

function Student(a, b) {
    this.name = a;
    this.id = b;
}

Student.prototype.age = 12;

const s1 = new Student("Dinesh", 1234567);

console.log(s1.name +
    " is " + s1.age + " years old.");

Output

Dinesh is 12 years old.

Example 2: This example adds a new method to the object.

Javascript

function Student(a, b) {
    this.name = a;
    this.id = b;
}

Student.prototype.details = function () {
    return this.name + " " + this.id
};

let s1 = new Student("Dinesh", 1234567);

console.log(s1.details());

Output

Dinesh 1234567