JavaScript Objects 🏗️

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JavaScript Objects 🏗️
Objects are key-value pairs used to store related data and functions.

1️⃣ Creating Objects
✅ 1. Using Object Literals {} (Most Common)

 

let person = {

    name: "Alice",

    age: 25,

    isStudent: false

};

console.log(person);

✅ 2. Using new Object() (Less Common)

let car = new Object();

car.brand = "Toyota";

car.model = "Corolla";

car.year = 2022;



console.log(car);

2️⃣ Accessing Object Properties
✅ 1. Dot Notation .

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

console.log(person.age);   // Output: 25

✅ 2. Bracket Notation []

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

let key = "age";

console.log(person[key]); // Output: 25

📌 Use bracket notation when keys are dynamic or contain spaces.

3️⃣ Modifying and Adding Properties

person.age = 30; // Modify

person.city = "New York"; // Add new property



console.log(person);

// { name: "Alice", age: 30, isStudent: false, city: "New York" }

4️⃣ Object Methods (Functions Inside Objects)

let person = {

    name: "Alice",

    greet: function() {

        console.log("Hello, my name is " + this.name);

    }

};



person.greet(); // Output: Hello, my name is Alice

📌 this refers to the current object (person).

5️⃣ The this Keyword
The this keyword refers to the object that is executing the function.

✅ 1. Inside an Object Method

let user = {

    name: "Bob",

    sayHi() {

        console.log("Hi, I'm " + this.name);

    }

};

user.sayHi(); // Output: Hi, I'm Bob

✅ 2. this in Global Scope

console.log(this); // Refers to `window` in browsers

✅ 3. this in Arrow Functions (No Own this)

let person = {

    name: "Alice",

    greet: () => {

        console.log("Hello, " + this.name);

    }

};

person.greet(); // Output: Hello, undefined

📌 Arrow functions do not bind this, so it refers to the global object (window).

6️⃣ Looping Through Objects
✅ 1. Using for...in

let car = {

    brand: "Toyota",

    model: "Corolla",

    year: 2022

};



for (let key in car) {

    console.log(key + ": " + car[key]);

}

// Output:

// brand: Toyota

// model: Corolla



// year: 2022

✅ 2. Using Object.keys(), Object.values(), Object.entries()

console.log(Object.keys(car));   // ["brand", "model", "year"]

console.log(Object.values(car)); // ["Toyota", "Corolla", 2022]

console.log(Object.entries(car)); // [["brand", "Toyota"], ["model", "Corolla"], ["year", 2022]]

7️⃣ Nested Objects
Objects can have other objects as values.

let student = {

    name: "John",

    scores: {

        math: 90,

        science: 85

    }

};

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

8️⃣ Summary
✅ Objects store key-value pairs.
✅ Access properties using . or [].
✅ Methods are functions inside objects.
✅ this refers to the current object.
✅ Use for...in or Object.keys() to loop through objects.

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    Date: 2025-03-29 00:00:00.000000