JavaScript Objects - Object Constructors

Object constructors are a way to create multiple instances of objects with similar properties and methods. In JavaScript, object constructors are functions that are used to construct and initialize objects. In this guide, we'll explore object constructors and provide examples to illustrate their usage.

Creating an Object Constructor

To create an object constructor, define a function and use the this keyword to set the properties of the object:

function Person(name, age) { = name;
this.age = age;
// Create instances of the Person object
const person1 = new Person("Alice", 30);
const person2 = new Person("Bob", 25);

In this example, we've created an object constructor called Person that takes name and age as parameters. We then create two instances of the Person object using the new keyword.

Adding Methods to Object Constructors

You can also add methods to object constructors. These methods are shared among all instances of the object:

function Car(make, model) {
this.make = make;
this.model = model;
this.start = function() {
console.log(`${this.make} ${this.model} is starting.`);
const car1 = new Car("Toyota", "Camry");
const car2 = new Car("Honda", "Civic");
car1.start(); // Outputs: "Toyota Camry is starting."
car2.start(); // Outputs: "Honda Civic is starting."

In this example, we've added a start method to the Car constructor that logs a message when the car starts.

Object Constructor Prototypes

Object constructors also have a prototype property, which can be used to add shared methods for all instances. This helps save memory and improve performance:

function Dog(name, breed) { = name;
this.breed = breed;
// Add a shared method using the prototype
Dog.prototype.bark = function() {
console.log(`${} (${this.breed}) is barking.`);
const dog1 = new Dog("Rover", "Golden Retriever");
const dog2 = new Dog("Buddy", "Labrador");
dog1.bark(); // Outputs: "Rover (Golden Retriever) is barking."
dog2.bark(); // Outputs: "Buddy (Labrador) is barking."

Using the prototype, the bark method is shared among all instances of the Dog object.


Object constructors provide a way to create and initialize objects with consistent properties and methods. By defining constructors and using the prototype, you can efficiently manage and manipulate objects in your JavaScript code. Understanding object constructors is essential for building structured and organized applications.

Happy coding with object constructors!