JavaScript Arrays

Arrays :

JavaScript arrays are special objects that store ordered collections of values in a single variable, supporting mixed data types and dynamic resizing. They enable efficient handling of lists like user data, DOM elements, or API responses in web development.

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Why Use Arrays?

Arrays group related data for easy access via zero-based indices (e.g., arr[0]), avoiding multiple variables like let a=1, b=2, c=3;.
They support built-in methods (push, map, filter) for common tasks like adding/removing items or transforming data, making code cleaner and scalable.
In dynamic apps, arrays handle variable-sized lists (e.g., shopping carts) without fixed limits, unlike primitives.

Now let's see the how we can create a simple array in JavaScript.

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Creation of an array :

We can create an array using various types of ways :

let favMovies = ["Inception", "Matrix", "Lucy"] //creation of an array.

let favMovies = new Array("Inception", "Matrix", "Lucy") //using "new" keyword

let numbers = new Array(3) //it will create 3 empty slots in an array.

let numbers = Array.of(3, 6, 9) //it will create array of these numbers instead of 3 empty slots.

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Accessing elements using index :

Accessing elements in an array uses square brackets [] with an index number—arrays start counting from 0, so first item is [0], second is [1], and so on.​

Basic Syntax

Declare array, then grab items by position: arrayName[index]. Reading or changing works the same way.

Example :

let favMovies = ["Inception", "Matrix", "Lucy"]
console.log(favMovies[1]) // "Matrix"
//Index starts from zero [0].

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Updating Elements :

You update array elements in JavaScript by assigning a new value directly to a specific index using square bracket notation array[index] = newValue.

Or

Adding any new value to the array.

let favMovies = ["Inception", "Matrix", "Lucy"]
favMovies[2] = "Interstellar" //["Inception", "Matrix", "Interstellar"]

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Array length property :

The array length property tells you exactly how many items are in your array—it's a read/write number you access with dot notation like array.length.

let favMovies = ["Inception", "Matrix", "Lucy", "Interstellar"]
console.log(favMovies.length) // 4

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Basic Looping over Arrays :

Basic looping over arrays repeats code for each item—like visiting every house on your street automatically.

For Loop (Most Control)

Classic way using index counter from 0 to length-1:

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