# JavaScript Arrays 101

When writing JavaScript programs, you often need to store **multiple values together**.

For example, imagine you want to store a list of fruits:

*   Apple
    
*   Mango
    
*   Banana
    
*   Orange
    

You could store them like this:

```plaintext
let fruit1 = "Apple";
let fruit2 = "Mango";
let fruit3 = "Banana";
let fruit4 = "Orange";
```

This works, but as the list grows, managing many variables becomes difficult.

This is where **arrays** become useful.

An **array** allows you to store multiple values in **a single structure**.

### 1\. What Arrays Are and Why We Need Them

An **array** is a collection of values stored **in a specific order**.

Instead of creating many variables, you can store everything inside one array.

Example:

```plaintext
let fruits = ["Apple", "Mango", "Banana", "Orange"];
```

Now all the fruit names are stored inside **one variable called** `fruits`.

Arrays are useful when working with:

*   lists of items
    
*   student marks
    
*   tasks in a to-do list
    
*   product collections
    

They help keep data **organized and easier to manage**.

### 2\. How to Create an Array

In JavaScript, arrays are created using **square brackets** `[]`.

Inside the brackets, values are separated by commas.

Example:

```plaintext
let fruits = ["Apple", "Mango", "Banana"];
```

You can also store numbers in an array.

Example:

```plaintext
let marks = [85, 90, 78, 92];
```

Or even a list of tasks:

```plaintext
let tasks = ["Study", "Exercise", "Read book"];
```

Each value inside an array is called an **element**.

### 3\. Accessing Elements Using Index

Every element in an array has a **position number**, called an **index**.

Important: **Array indexing starts from 0**.

Example array:

```plaintext
let fruits = ["Apple", "Mango", "Banana"];
```

Index positions:

| index | value |
| --- | --- |
| 0 | Apple |
| 1 | Mango |
| 2 | Banana |

To access an element, use its index.

Example:

```plaintext
console.log(fruits[0]); 
```

Output:

```plaintext
Apple
```

Another example:

```plaintext
console.log(fruits[2]);
```

Output:

```plaintext
Banana
```

### 4\. Updating Elements

You can also **change values inside an array**.

Example:

```plaintext
let fruits = ["Apple", "Mango", "Banana"];

fruits[1] = "Orange";
```

Now the array becomes:

```plaintext
["Apple", "Orange", "Banana"]
```

Here we replaced **Mango with Orange**.

Updating elements is helpful when data **changes over time**.

### 5\. Array Length Property

JavaScript arrays have a built-in property called `length`.

It tells you **how many elements are inside the array**.

Example:

```plaintext
let fruits = ["Apple", "Mango", "Banana", "Orange"];

console.log(fruits.length);
```

Output:

```plaintext
4
```

This is useful when working with loops or checking how many items exist in a list.

### 6\. Basic Looping Over Arrays

Often you want to **go through every item in an array**.

This can be done using a **loop**.

Example using a `for` loop:

```plaintext
let fruits = ["Apple", "Mango", "Banana"];

for (let i = 0; i < fruits.length; i++) {
  console.log(fruits[i]);
}
```

Output:

```plaintext
Apple
Mango
Banana
```

Here:

*   `i` represents the index number
    
*   The loop runs until it reaches the array length
    

This allows you to process **every element in the array**.

### Why Arrays Are Useful

Arrays help you:

*   store multiple values in one place
    
*   organize data in order
    
*   easily access items using indexes
    
*   loop through collections of data
    

They are commonly used in things like:

*   product lists in websites
    
*   user data
    
*   to-do applications
    
*   game scores