JavaScript Objects

Table of Contents

• Intro
• What is an Object?
• Accessing Properties
• Modifying Properties
• Deleting Properties
• Object Methods
• Looping Through Objects
• Nested Objects
• Object vs Array
• Visual Understanding
• Real-Life Example
• Important Methods
• Best Practices
• When to Use Objects
• Interview Q&A
• MCQ

JavaScript Objects Tutorial (Beginner -> Practical)

Objects are one of the most important data structures in JavaScript. They allow you to store data in key-value pairs, making them ideal for representing real-world entities like users, products, or settings.

1. What is an Object?

An object groups related data and behavior.

let person = {
    name: "John",
    age: 25,
    isStudent: false
};

console.log(person);

Here, name, age, isStudent are keys and their assigned data are values.

2. Accessing Object Properties

Dot Notation

console.log(person.name);
console.log(person.age);

Bracket Notation

console.log(person["name"]);

Bracket notation is useful when the key is dynamic.

3. Modifying Object Properties

person.age = 30;          // update
person.city = "Delhi";    // add new property

console.log(person);

4. Deleting Properties

delete person.isStudent;

5. Object Methods (Functions inside Objects)

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

person.greet();

this refers to the current object.

6. Looping Through Objects

let person = {
    name: "John",
    age: 25
};

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

7. Nested Objects

Objects inside objects.

let student = {
    name: "Ravi",
    marks: {
        math: 90,
        science: 85
    }
};

console.log(student.marks.math);

8. Object vs Array

9. Visual Understanding

Objects store data in named key-value format, which makes them readable and useful for entity-style data.

10. Real-Life Example

let product = {
    name: "Laptop",
    price: 50000,
    inStock: true
};

if (product.inStock) {
    console.log(product.name + " is available");
}

11. Important Methods

let person = { name: "John", age: 25 };

console.log(Object.keys(person));   // ["name", "age"]
console.log(Object.values(person)); // ["John", 25]
console.log(Object.entries(person));// [["name","John"],["age",25]]

12. Best Practices

• Use meaningful property names.
• Prefer dot notation unless keys are dynamic.
• Avoid deeply nested objects unless necessary.
• Keep objects structured and readable.

13. When to Use Objects

Use objects when you need to represent user profiles, product details, API data, or configuration settings.

Related Topics

Arrays, Functions, and DOM Basics rely heavily on object structures in day-to-day JavaScript.

10 Objects Interview Q&A

10 Objects MCQs