# Understanding Objects in JavaScript

If you've been working with JavaScript, you've probably used arrays to store lists of data. But what happens when you need to store more complex, structured information? That's where **objects** come in.

As we continue our journey through the Web Dev Cohort 2026, understanding objects is a massive stepping stone toward becoming a full-stack engineer. Let's break down what objects are, why we need them, and how to use them.

* * *

## What Are Objects and Why Do We Need Them?

Imagine you want to store information about a person. You *could* use an array:

```javascript
let personArray = ["Divyanshu", 25, "Delhi"];
```

But there's a problem here. Looking at `personArray[1]`, how do you know if `25` is the person's age, their lucky number, or their house number? An array is just an ordered list; it doesn't give us context.

An **object** solves this by storing data in a **key-value pair** structure. Instead of relying on an index (like 0, 1, or 2), you use a descriptive "key" (a label) to store and access a "value".

* * *

## Creating Objects

Creating an object is straightforward. We use curly braces `{}` and define our key-value pairs inside them.

```javascript
let person = {
  name: "Divyanshu",
  age: 25,
  city: "Delhi"
};
```

Now, the data is perfectly clear. The key is `name` and the value is `"Divyanshu"`.

* * *

## Accessing Properties

To get information out of an object, you have two main options: **Dot Notation** and **Bracket Notation**.

### 1\. Dot Notation

This is the most common and easiest way to access a property. You just write the object name, a dot, and the key.

```javascript
console.log(person.name); // Output: Divyanshu
console.log(person.city); // Output: Delhi
```

### 2\. Bracket Notation

Sometimes you need to use bracket notation. This is especially useful if your key has a space in it (which isn't recommended, but possible) or if you are using a variable to access the key.

```javascript
console.log(person["age"]); // Output: 25

let propertyToCheck = "city";
console.log(person[propertyToCheck]); // Output: Delhi
```

* * *

## Modifying Objects: Updating, Adding, and Deleting

Objects are dynamic. You can change them even after you've created them.

### Updating Properties

To change an existing value, just reassign it using dot or bracket notation.

```javascript
person.age = 26;
console.log(person.age); // Output: 26
```

### Adding New Properties

Adding a new property is just as easy. Simply assign a value to a key that doesn't exist yet.

```javascript
person.profession = "Developer";
console.log(person); 
// Output: { name: 'Divyanshu', age: 26, city: 'Delhi', profession: 'Developer' }
```

### Deleting Properties

If you need to remove a property completely, use the `delete` keyword.

```javascript
delete person.city;
console.log(person); 
// Output: { name: 'Divyanshu', age: 26, profession: 'Developer' }
```

* * *

## Looping Through Object Keys

Sometimes you want to go through all the properties in an object, maybe to print them out to the console. Because objects aren't ordered like arrays, we use a special loop called the `for...in` loop.

```javascript
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
```

*Notice how we used* `car[key]` *(bracket notation) inside the loop. If we used* `car.key`*, JavaScript would look for a property literally named "key", which doesn't exist!*

* * *

## 📝 Try It Yourself! (Assignment Idea)

Ready to put this into practice? Here is a quick challenge to test your skills:

1.  Create an object representing a `student`.
    
2.  Add the following properties: `name`, `age`, and `course`.
    
3.  Update the `course` property to a new subject.
    
4.  Print all the keys and their corresponding values using a `for...in` loop.
    

The END :).