JavaScript Objects

JavaScript objects are collections of key-value pairs, where the keys are strings and the values can be of any type. They are fundamental in JavaScript for organizing and managing data.

1. Creating Objects

You can create objects using object literals or the Object constructor.

Object Literal

const person = {
    name: "John",
    age: 30,
    greet: function() {
        return "Hello, " + this.name;
    }
};

            

Here, person is an object with properties name, age, and a method greet.

Object Constructor

const person = new Object();
person.name = "John";
person.age = 30;
person.greet = function() {
    return "Hello, " + this.name;
};

            

This method is less common but demonstrates how you can add properties to an object created with the Object constructor.

2. Accessing and Modifying Object Properties

You can access and modify object properties using dot notation or bracket notation.

Dot Notation

console.log(person.name); // "John"
person.age = 31;

            

Bracket Notation

console.log(person["name"]); // "John"
person["age"] = 31;

            

3. Object Methods

Object methods are functions that are properties of an object. They can be defined using either traditional function syntax or ES6 arrow functions.

Traditional Method

const person = {
    name: "John",
    greet: function() {
        return "Hello, " + this.name;
    }
};
console.log(person.greet()); // "Hello, John"

            

ES6 Method

const person = {
    name: "John",
    greet() {
        return "Hello, " + this.name;
    }
};
console.log(person.greet()); // "Hello, John"

            

4. The this Keyword

this refers to the current object in method calls. It allows access to the object's properties and methods from within the method itself.

const person = {
    name: "John",
    greet() {
        return "Hello, " + this.name;
    }
};
console.log(person.greet()); // "Hello, John"

            

5. Object Prototypes

JavaScript objects have a prototype chain that allows them to inherit properties and methods from other objects.

// Creating a prototype
const animal = {
    eats: true
};

// Creating an object that inherits from animal
const dog = Object.create(animal);
console.log(dog.eats); // true

            

In this example, dog inherits the eats property from the animal prototype.