What Is An Array ?

An arrays is simply a data structure which helps to store collection of items or multiple values in a single variable. In other programming languages like C, C++ or Java. Array can store items which are of similar data type. But in JavaScript Array can store items with dissimilar data type in a same variable.

Why we need an array?

Suppose you want to store the list of 10 fruits that you like. Assigning a single variable for a fruit is lengthy and it takes a lot of time and variable names. Instead we use array to store multiple values in a single variable. For example:-

// Storing list of 3 fruits name in an array
let fruitsILike = ["Apple", "Orange", "Banana"] ;

Adding Items In An Array

1. Adding Items In The End

You can use push() function or method to add items at the end of an array.

let numbers = [1,2,3];
numbers.push(4,5); // 4 and 5  will be added at the last
console.log(numbers);

2. Adding Items In The Beginning

If you want to add items at the beginning of an array you use unshift() function.

let numbers = [1,2,3];
numbers.unshift(0,-1); // adds 0 and -1 at the beginning of an array
console.log(numbers);

3. Adding Items In The Middle

splice() method is used to add new elements in an array or remove elements from an array. It has 3 parameters. 1st parameter is starting position. 2nd parameter is delete count. 3rd parameter lets you add items an array.

let months = ["Jan", "Feb", "May", "June"];
months.splice(2, 0, "March", "April"); // 2 is the position where we want to start from , 0 is the no of items we want to delete, "March" and "April" are items that you want to add
console.log(months); // Prints [ 'Jan', 'Feb', 'March', 'April', 'May', 'June' ]

Deleting Items In An Array

To delete items in an array we have 3 methods - pop(), shift(), splice().

1. Deleting Items From End

We use pop() method to delete last item in an array.

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

2. Deleting From Front

We use shift() method to delete items which are at first position.

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

3. Deleting From Middle

We use splice() method to delete items from middle or any position or index that we like. It has 2 parameters. 1st parameter is starting position. 2nd parameter is delete count.

let fruits = ["Apple", "Mango", "Orange", "Grapes", "Watermelon"];
fruits.splice(2, 1); // 2 is the starting index and 1 is the number of items to be deleted
console.log(fruits); // Output [ 'Apple', 'Mango', 'Grapes', 'Watermelon' ]

Emptying An Array

There are multiple ways to empty an array, out of which we are going to look only 2 ways to empty an array.

// 1st method
let fruits = ["Apple","Mango", "Orange"];
fruits = [];
cosole.log(fruits); // here array will be empty

//2nd method
let ages = [20, 35, 90];
ages.length = 0;
console.log(ages); // Here array will be empty

Array Concatenation

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

let fruits = ["Apple", "Mango", "Orange", "Grapes", "Watermelon"];
let ages = [20, 40, 80, 30];

let newArray = ages.concat(fruits); 
console.log(newArray);// Output = [ 20, 40, 80, 30, 'Apple', 'Mango', 'Orange', 'Grapes', 'Watermelon' ]