Array in JavaScript

Array
An Array is a collection of multiple values stored in a single variable.

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

Here, fruits contains three values.

Why Do We Need Arrays?
Without an array, you would write:

let fruit1 = "Apple";
let fruit2 = "Mango";
let fruit3 = "Orange";

Using an array:

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

This makes the code shorter and easier to manage.

Array Index
Each value in an array has an index. The index always starts from 0.

Index:   0        1         2
        -------------------------
Array:  Apple   Mango   Orange

Accessing Array Elements
Use the index number to access a value.

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

console.log(fruits[0]);
console.log(fruits[1]);
// Output:
Apple
Mango

Changing an Array Element
You can update any value using its index.

let fruits = ["Apple", "Mango", "Orange"];
fruits[1] = "Banana";
console.log(fruits);
// Output:
["Apple", "Banana", "Orange"]

Finding the Length of an Array
Use the "length" property.

let fruits = ["Apple", "Mango", "Orange"];
console.log(fruits.length);
// Output: 3

Adding Elements

1. push() – Add at the End

let fruits = ["Apple", "Mango"];
fruits.push("Orange");
console.log(fruits);
// Output: ["Apple", "Mango", "Orange"]

1. unshift() – Add at the Beginning

let fruits = ["Mango", "Orange"];
fruits.unshift("Apple");
console.log(fruits);
// Output: ["Apple", "Mango", "Orange"]

Removing Elements

1. pop() – Remove from the End

let fruits = ["Apple", "Mango", "Orange"];
fruits.pop();
console.log(fruits);
// Output: ["Apple", "Mango"]

1. shift() – Remove from the Beginning

let fruits = ["Apple", "Mango", "Orange"];
fruits.shift();
console.log(fruits);
// Output: ["Mango", "Orange"]

Looping Through an Array
Use a "for loop" to print all elements.

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

for (let i = 0; i < fruits.length; i++) {
    console.log(fruits[i]);
}
// Output:
Apple
Mango
Orange

"for...of" is an easier way to loop through an array.

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

for (let fruit of fruits) {
    console.log(fruit);
}
// Output:
Apple
Mango
Orange

Common Array Methods

1. includes() - Checks whether an element exists.

let fruits = ["Apple", "Mango", "Orange"];
console.log(fruits.includes("Mango"));
// Output: true

1. indexOf() - Returns the index of an element.

let fruits = ["Apple", "Mango", "Orange"];
console.log(fruits.indexOf("Orange"));
// Output: 2

1. join() - Joins all elements into a single string.

let fruits = ["Apple", "Mango", "Orange"];
console.log(fruits.join(", "));
// Output: Apple, Mango, Orange

1. reverse() - Reverses the array.

let fruits = ["Apple", "Mango", "Orange"];
fruits.reverse();
console.log(fruits);
// Output: ["Orange", "Mango", "Apple"]

1. sort() - Sorts the array.

let fruits = ["Orange", "Apple", "Mango"];
fruits.sort();
console.log(fruits);
// Output: ["Apple", "Mango", "Orange"]

Array with Different Data Types
An array can store different types of values.

let data = ["Pranay", 21, true, 95.5];
console.log(data);

Nested Arrays
An array can also contain another array.

let numbers = [
    [1, 2],
    [3, 4]
];

console.log(numbers[1][0]);
// Output: 3