JavaScript Arrays 101

When learning JavaScript, one big question appears:

What if I want to store multiple values together?

That's where arrays come in.

What Are Arrays?

Imagine we want to store a list of fruits:

• Apple

• Banana

• Mango

• Orange

Without arrays, we would do something like this:

let fruit1 = "apple";
let fruit2 = "banana";
let fruit3 = "mango";
let fruit4 = "orange";

This works, but what if we had 100 fruits?

That's where arrays come in.

What is an Array and Why do we Need Them?

An array is a collection of values stored in order.

Instead of creating many variables, we store multiple values inside a single variable.

Think of an array like box that holds multiple items.

How To Create An Array?

In JavaScript, we create arrays using square brackets [] .

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

Now all fruit names are stored inside one variable: fruits .
Simple. Clean. Powerful.

Accessing Elements Using Index

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

Important: Indexing starts from 0.

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

console.log(fruits[0]); // Apple
console.log(fruits[1]); // Banana

So the position look like this:

Index	Value
0	Apple
1	Banana
2	Mango
3	Orange

Updating Elements

We can change any value using its index.

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

fruits[1] = "Grapes";

console.log(fruits);
// ["Apple", "Grapes", "Mango", "Orange"]

We simply assign the new value to that index.

The Array Length Property

JavaScript gives us a built-in property called length .

It tells us how many elements are inside the array.

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

console.log(fruits.length); // 4

This is extremely useful when looping.

Basic Looping Over Arrays:

To print all elements, we can use a simple for loop:

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

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

How it works:

• Starts from index 0

• Run until i < fruits.length

• Print each element.

This is the most basic and important way to loop over arrays.

Why Arrays Are Better Than Individual Variables

Without Array:

let mark1 = 85;
let mark2 = 90;
let mark3 = 78;

Hard to manage and loop through.

With Arrays:

let marks = [85, 90, 78];

Now we can loop, update, count -- all easily.

Arrays make our code:

• Cleaner

• Shorter

• Easier to maintain

• More scalable

Assignment Practice

(Try to solve on your own)

Task 1: Create an array of your 5 favorite movies

let movies = ["Movie1", "Movie2", "Movie3", "Movie4", "Movie5"];

Task 2: Print the first and last element.

console.log(movies[0]); 
console.log(movies[movies.length - 1]);

Task 3: Change one value and print updated array

movies[2] = "New Movie Name";

console.log(movies);

Task 4: Loop through the array and print all elements.

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

Final Thoughts

Arrays are one of the most important building blocks in JavaScript.

Once you understand:

• Creating Arrays

• Indexing

• Updating values

• Using length

• Looping

You've build a strong foundation.