JavaScript is a flexible object-oriented language when it comes to syntax. In this article, we will see the different ways to instantiate objects in JavaScript. Before we proceed it is important to note that JavaScript is an object-based language based on prototypes, rather than being class-based. Because of this different basis, it can be less apparent how JavaScript allows you to create hierarchies of objects and to have an inheritance of properties and their values.
Creating object with a constructor:
One of the easiest ways to instantiate an object is in JavaScript. Constructor is nothing but a function and with help of a new keyword, the constructor function allows to create of multiple objects of the same flavor as shown below:
javascript
// Simple function function vehicle(name,maker,engine){ this.name = name; this.maker = maker; this.engine = engine; } // New keyword to create an object let car = new vehicle('GT','BMW','1998cc'); // Property accessors console.log(car.name); console.log(car.maker); console.log(car['engine']); |
Output:
GT BMW 1998cc
Explanation: A class in OOPs have two major components, certain parameters and few member functions. In this method we declare a function similar to a class, there are three parameters, name, maker and engine ( the this keyword is used to differentiate the name,maker,engine of the class to the name,maker,engine of the arguments that are being supplied.). We then simple create an object obj of the vehicle, initialize it and call it’s method.
Using object literals:
Literals are smaller and simpler ways to define objects. We simply define the property and values inside curly braces as shown below:
javascript
// Creating js objects with object literal let car = { name : 'GT', maker : 'BMW', engine : '1998cc'}; // Property accessor console.log(car.name); //dot notation console.log(car['maker']); //bracket notation |
Output:
GT BMW
In the above code, we created a simple object named car with the help of object literal,having properties like name,maker,engine.Then we make use of the property accessor methods(Dot notation,Bracket notation) to console.log the values. Now let’s see how we can add more properties to an already defined object:
javascript
let car = { name : 'GT', maker : 'BMW', engine : '1998cc'}; // Adding property to the object car.brakesType = 'All Disc'; console.log(car); |
Output:
{name: 'GT', maker: 'BMW', engine: '1998cc', brakesType: 'All Disc'}
Methods can also be part of the object while creation or can be added later like properties as shown below:
javascript
// Adding methods to the car object let car = { name : 'GT', maker : 'BMW', engine : '1998cc', start : function(){ console.log('Starting the engine...'); } }; car.start(); // Adding method stop() later to the object car.stop = function() { console.log('Applying Brake...'); } car.stop(); |
Output:
Starting the engine... Applying Brake...
Explanation: In the above code start method was added to the car object and later called by the car.start() and also the stop method was added too after the object was already declared.
Creating object with Object.create() method:
The Object.create() method creates a new object, using an existing object as the prototype of the newly created object. Example:
javascript
const coder = { isStudying : false, printIntroduction : function(){ console.log(`My name is ${this.name}. Am I studying?: ${this.isStudying}`); } }; const me = Object.create(coder); me.name = 'Mukul'; me.isStudying = true; me.printIntroduction(); |
Output:
My name is Mukul. Am I studying?: true
Using es6 classes: ES6 supports class concept like any other Statically typed or object oriented language. So, object can be created out of a class in javascript as well as shown below:
javascript
// Using es6 classes class Vehicle { constructor(name, maker, engine) { this.name = name; this.maker = maker; this.engine = engine; } } let car1 = new Vehicle('GT', 'BMW', '1998cc'); console.log(car1.name); //GT |
Output:
GT
