JAVASCRIPT PART 7 || JavaScript Object Introduction

EBS

Summary

Creating a JavaScript Object
With JavaScript, you can define and create your own objects.

There are different ways to create new objects:

Create a single object, using an object literal.
Create a single object, with the keyword new.
Define an object constructor, and then create objects of the constructed type.
Create an object using Object.create().

Using an Object Literal
This is the easiest way to create a JavaScript Object.

Using an object literal, you both define and create an object in one statement.

An object literal is a list of name:value pairs (like age:50) inside curly braces {}.

The following example creates a new JavaScript object with four properties:

Example
const person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};

Using the JavaScript Keyword new
The following example create a new JavaScript object using new Object(), and then adds 4 properties:

Example
const person = new Object();
person.firstName = "John";
person.lastName = "Doe";
person.age = 50;
person.eyeColor = "blue";

JavaScript Objects are Mutable
Objects are mutable: They are addressed by reference, not by value.

If person is an object, the following statement will not create a copy of person:

const x = person; // Will not create a copy of person.
The object x is not a copy of person. It is person. Both x and person are the same object.

Any changes to x will also change person, because x and person are the same object.

Example
const person = {
firstName:"John",
lastName:"Doe",
age:50, eyeColor:"blue"
}

const x = person;
x.age = 10; // Will change both x.age and person.age