🧠 10-Day JS Challenge: Objects & Nested Data Day-7

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📅 Day 7: Objects & Nested Data

Welcome to Day 7 of the challenge!

Today we're diving into objects—a key data structure in JavaScript that helps us store data in the form of key-value pairs. Objects are perfect for representing real-world entities like users, products, or configurations.

🧩 What is an Object?
An object is a collection of related data and functions (called properties and methods). Each property is a key-value pair.

let user = {
  name: "Smriti",
  age: 24,
  isMember: true
};

🔍 Accessing Object Properties
You can access object properties in two ways:

1. Dot Notation

console.log(user.name); // Smriti

2. Bracket Notation

console.log(user["age"]); // 24

Bracket notation is useful when:

The key is stored in a variable
The key has spaces or special characters

🧱 Updating & Adding Properties

user.name = "Aarav";          // Update
user.email = "aarav@email.com"; // Add

You can also delete properties:

delete user.isMember;

🧭 Nested Objects and Arrays
Objects can contain other objects and arrays — making it easy to model complex data.

let student = {
  name: "Ananya",
  age: 18,
  subjects: ["Math", "Science", "English"],
  address: {
    city: "Delhi",
    pin: 110001
  }
};

console.log(student.subjects[1]);       // "Science"
console.log(student.address.city);      // "Delhi"

❄️ Using Object.freeze() to Lock an Object
If you want to make an object read-only, use Object.freeze().

const settings = {
  theme: "dark",
  fontSize: 16
};

Object.freeze(settings);

settings.theme = "light"; // Ignored!
console.log(settings.theme); // "dark"

Note: Object.freeze() only works at the top level — nested objects remain mutable unless you recursively freeze them.

✅ Mini Task: Create and Print a Student Object
🎯 Task:
Create a student object with:

name
age
subjects (an array)
address (nested object with city and pin)
Print the information neatly.

💻 Example:

const student = {
  name: "Aarav",
  age: 20,
  subjects: ["Math", "Physics", "Chemistry"],
  address: {
    city: "Mumbai",
    pin: 400001
  }
};

Object.freeze(student);

console.log("Name:", student.name);
console.log("Age:", student.age);
console.log("Subjects:", student.subjects.join(", "));
console.log("City:", student.address.city);
console.log("PIN Code:", student.address.pin);

❓ Interview Questions (Day 7 Topics)