When writing programs, we often need to store multiple values together.

For example, imagine you want to store:

• A list of fruits

• A student's marks

• A list of tasks

One way is to create separate variables:

let fruit1 = "apple";
let fruit2 = "banana";
let fruit3 = "mango";

But this quickly becomes messy and hard to manage.

A better solution is to store all values inside a single structure called an array.

In this article, we will learn:

• What arrays are and why we need them

• How to create an array

• How to access elements using index

• How to update elements

• The array length property

• Basic looping over arrays

All examples are simple so you can try them in your browser console or Node.js.

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What Are Arrays?

An array is a collection of values stored in order.

Instead of creating multiple variables, we store the values inside one array.

Example:

let fruits = ["apple", "banana", "mango"];

Here the array contains three values.

Output:

["apple", "banana", "mango"]

So instead of writing many variables, we use one array to store multiple items.

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Creating an Array

Arrays are created using square brackets [].

Example:

let numbers = [10, 20, 30, 40];

Example with strings:

let fruits = ["apple", "banana", "mango"];

Arrays can also contain different types of values:

let data = ["Alex", 25, true];

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Accessing Array Elements

Each element in an array has a position number called an index.

Important rule:

Array indexing starts from 0

Example:

let fruits = ["apple", "banana", "mango"];

Index positions:

0 → apple
1 → banana
2 → mango

Accessing elements:

console.log(fruits[0]);
console.log(fruits[1]);

Output:

apple
banana

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Updating Array Elements

We can change an element in an array by using its index.

Example:

let fruits = ["apple", "banana", "mango"];

fruits[1] = "orange";

console.log(fruits);

Output:

["apple", "orange", "mango"]

Here the value banana was replaced with orange.

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The Array length Property

The length property tells us how many elements are in the array.

Example:

let fruits = ["apple", "banana", "mango"];

console.log(fruits.length);

Output:

3

This is very useful when working with loops.

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Looping Over Arrays

Often we want to go through every element in an array.

We can do this using a for loop.

Example:

let fruits = ["apple", "banana", "mango"];

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

Output:

apple
banana
mango

How it works:

1. i starts from 0

2. The loop runs while i < fruits.length

3. Each iteration prints fruits[i]

So the loop accesses every element in the array.

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Practical Example

Example with student marks:

let marks = [75, 82, 90, 68];

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

Output:

75
82
90
68

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Arrays are one of the most important data structures in JavaScript.

They allow us to store multiple values in a single variable and work with them easily.

Key things to remember:

• Arrays store multiple values in order

• They are created using square brackets []

• Elements are accessed using indexes starting from 0

• The length property tells the number of elements

• Loops help us process every item in an array