JavaScript Object & it's Methods

What is Object in JavaScript ?

In JavaScript, an object is a fundamental data type that allows developers to store collections of key-value pairs. It's a versatile and dynamic entity used to represent real-world entities, data structures, and more complex entities in the language. Objects in JavaScript are a cornerstone of the language's flexibility and are used extensively across various applications.

Properties of JavaScript Objects:

1. Key-Value Pairs:

   • An object consists of key-value pairs where the key is a string and the value can be any data type: primitives, objects, functions, etc.

       let person = {
         name: 'John',
         age: 30,
         city: 'New York'
       };
     

2. Dynamic Nature:

   • Objects in JavaScript are mutable, meaning their properties can be added, updated, or deleted after creation.

    javascriptCopy codeperson.email = 'john@example.com'; 
                          // Adding a new property
    person.age = 31;     // Updating an existing property
    delete person.city; // Deleting a property

1. Accessing Object Properties:

   • Properties of an object can be accessed using dot notation or bracket notation.

    console.log(person.name);   // Output: 'John'
    console.log(person['age']); // Output: 31

1. Object Methods:

   • Objects can contain functions as values, which are referred to as methods.

    let car = {
      brand: 'Toyota',
      year: 2020,
      start: function() {
        console.log('Engine started');
      }
    };
    car.start(); // Output: 'Engine started'

1. Object Constructors:

   • JavaScript also allows object creation using constructor functions or class syntax.

       // Constructor function
       function Person(name, age) {
         this.name = name;
         this.age = age;
       }
       let person1 = new Person('Alice', 25);
     

Object as a Reference Type:

In JavaScript, objects are reference types. When assigned to a variable or passed as an argument, they are passed by reference, meaning the variable holds a reference (address) to the object in memory, not the object itself.

let obj1 = { name: 'John' };
let obj2 = obj1; // obj2 now references the same object as obj1

obj2.name = 'Jane';
console.log(obj1.name); // Output: 'Jane' (Both obj1 and obj2 reference the same object)

The Object Prototype:

Each object in JavaScript has a prototype from which it inherits methods and properties. The prototype property allows you to add properties and methods to an object.

let student = {
  name: 'Alice',
  age: 20
};

// Adding a new method to the prototype
Object.prototype.greet = function() {
  console.log(`Hello, my name is ${this.name}.`);
};

student.greet(); // Output: 'Hello, my name is Alice.'

In essence, objects in JavaScript provide a powerful and flexible way to store and manipulate data, making them a fundamental aspect of the language's functionality and versatility.