Javascript Objects

JavaScript Objects

🔹 What is an Object?

In JavaScript, an object is a collection of key-value pairs, where the keys (properties) are strings and the values can be of any data type (strings, numbers, arrays, functions, etc.). Objects allow you to store and organize data efficiently.

🔹 Creating an Object

Objects can be created in multiple ways:

1️⃣ Object Literal (Most Common)

let person = {
    name: "Alice",
    age: 25,
    isStudent: true
};

console.log(person.name); // Output: Alice
console.log(person.age); // Output: 25
console.log(person.isStudent); // Output: true

2️⃣ Using `new Object()` (Less Common)

let person = new Object();
person.name = "Alice";
person.age = 25;

console.log(person.name); // Output: Alice

🔹 Accessing Object Properties

You can access object properties in two ways:

console.log(person.name);    // Dot notation → Output: Alice
console.log(person["age"]);  // Bracket notation → Output: 25

💡 Use bracket notation when property names have spaces or special characters.

🔹 Adding & Modifying Properties

person.city = "New York"; // Adding new property
person.age = 30; // Modifying property

console.log(person.city); // Output: New York
console.log(person.age); // Output: 30

🔹 Removing Properties

delete person.isStudent;
console.log(person.isStudent); // Output: undefined

🔹 Object with Methods (Functions Inside an Object)

An object can contain methods (functions as properties).

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

car.start(); // Output: The car has started.

🔹 Shorter Method Syntax (ES6)

🔹 Looping Through an Object (`for...in` Loop)

To iterate over object properties:

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

🔹 Nested Objects (Objects Inside Objects)

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

console.log(student.marks.math); // Output: 90

🔹 Checking If a Property Exists

console.log(Object.keys(person));   // Output: ["name", "age", "city"]
console.log(Object.values(person)); // Output: ["Alice", 30, "New York"]
console.log(Object.entries(person));// Output: [["name", "Alice"], ["age", 30], ["city", "New York"]]

🔹 Conclusion

Objects store key-value pairs.
Properties are accessed via dot notation or bracket notation.
Objects can contain methods (functions).
Use loops and built-in methods to manipulate objects efficiently.

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