Object in JavaScript is a collection of key-value pairs. It is used to store multiple values ​​in a structured manner.

Syntax:

let objectName = {
   key1: value1,
   key2: value2,
   key3: value3
};

• Key → Property name (string)
• Value → Can be string, number, boolean, array, function, or any other object.

 

Creating an Object

 

Using Object Literal (Most Common)

let person = {
   name: "John",
   age: 30,
   city: "New York"
};
console.log(person);  // { name: "John", age: 30, city: "New York" }

Accessing Object Properties

• Using Dot Notation (.)

console.log(person.name);  // "John"
console.log(person.age);   // 30

• Using Bracket Notation ([])

console.log(person["name"]);  // "John"
console.log(person["age"]);   // 30

 

Use bracket notation when property names have spaces or special characters

let obj = { "first name": "John" };
console.log(obj["first name"]);  // "John"

Adding & Updating Properties

 

Adding a New Property

person.country = "USA";
console.log(person.country);  // "USA"

Updating an Existing Property

person.age = 35;
console.log(person.age);  // 35

 

Deleting a Property

delete person.city;
console.log(person.city);  // undefined

 

Checking if a Property Exists

 

Using in Operator

console.log("age" in person);  // true
console.log("city" in person); // false

Using hasOwnProperty()

console.log(person.hasOwnProperty("name"));  // true
console.log(person.hasOwnProperty("city"));  // false

 

Looping Through an Object

Using for...in loop

for (let key in person) {
   console.log(key + ": " + person[key]);
}

Output:

name: John
age: 35
country: USA

 

Nested Objects

Objects can also contain other objects.

let student = {
   name: "Alice",
   marks: {
       math: 90,
       science: 85
   }
};
console.log(student.marks.math);  // 90
console.log(student["marks"]["science"]);  // 85

 

Object Methods (Functions Inside Objects)

An object method is a function that is stored inside an object.

let car = {
   brand: "Toyota",
   model: "Corolla",
   start: function() {
       return "Car started";
   }
};
console.log(car.start());  // "Car started"

 

this Keyword in Objects

this refers to the current object.

let user = {
   name: "Alex",
   greet: function() {
       return "Hello, " + this.name;
   }
};
console.log(user.greet());  // "Hello, Alex"

 

Creating Objects Using new Object()

let car = new Object();
car.brand = "Ford";
car.model = "Mustang";
console.log(car.brand);  // "Ford"

Summary

• Objects store data as key-value pairs.
• Methods are functions inside the object.
• Use the dot (.) or bracket ([]) notation to access properties.
• Use a for...in loop to iterate over the object.
• Use this to refer to the current object.

 

I hope you understand clearly the javascript objects.

Thanks.

 

Also, read: JavaScript Loops Explanation