What is Array ?

We can store more than one elements in a single variable.
One of the representation of input in the form of collection of elements or items.

How is Array defined in Javascript ?

Its defined in pair of square brackets [ ]
All the elements are provided inside this pair of square brackets with comma separated.
Element can be of any data type in the array.(String,Number,Boolean,Objects etc)
Eg: let arrVariable = [1, "Hello", true];

First element in the array has an index value as 0.

Note : What is index ? Position of the array element within the array.

No of elements/items in a array is nothing but its size. JS arrays are not fixed in size.

Points to remember about arrays.

Stored as Objects.

Consider :

let myArray1 = [1,2,3,4];

let myArray2 = [1,2,3,4];

myArray1 === myArray2 //  returns false

Why return false ?

ts placing myArray1 and myArray2 in different memory locations.

Now Consider this situation

let myArray1 = [1,2,3,4];
let myArray2 = myArray1;

myArray1 === myArray2 //  returns true

Why return true ?

myArray2 is just pointing to myArray1 in memory.

Note : if we reassign myArray2 to different elements it will point to diffferent memory.

How elements are accessed in the array ?

You can access the element from an array using its index.

const element = myArray[index];

You can access and loop through each element in an array by for, and for of and .forEach method(will be covered later).

How to Insert/Delete/Edit Elements in an array ?

A. At the Beginning. [INSERT]

We use the unshift() method to insert an element into an array in the beginning.

let myArray1 = [1,2,3,4];
myArray1.unshift(0);  // Output : [0,1,2,3,4]

B. At the End. [INSERT]

We use the push() method to insert an element into an array. The push() method adds an element at the end of the array.

let myArray1 = [1,2,3,4];
myArray1.push(5); //returns the last position of the array Output [1,2,3,4,5]

C. Anywhere. [INSERT]

We use the splice() method to insert an element into an array anywhere. for example if we want to insert 2.5 next to 2 which is at index 2.follow the below steps

let myArray1 = [1,2,3,4];
myArray1.splice(2,0,2.5); //First argument starting index, second : delete count =0 and Insert 2.5 in the second index of the array Output [1,2,2.5,3,4]

Note : if we give more elements next to 2.5 it will be inserted

D. At the Beginning. [REMOVE]

We use the shift() method to remove an element into an array in the beginning.

let myArray1 = [1,2,3,4];
myArray1.shift(); //Output after shift() method : [2,3,4]

E. At the End. [REMOVE]

We use the pop() method to remove an element into an array.

let myArray1 = [1,2,3,4];
myArray1.pop(); //returns the deleted position of the array After pop method : [1,2,3]

F. Anywhere [REMOVE]

we can use splice() method It can do insert, remove and replace elements. now we can first see remove

arr.splice(start[, deleteCount, elem1, ..., elemN])

const array = [10,20,30,40];

If we want to remove 20 which is at index 1

arr.splice(1,1); //From index 1 remove element only 1(2nd argument).

G. Anywhere [EDIT]

we can use splice() method It can do insert, remove and replace elements. now we can edit the element. we can replace element 20 with 21

arr.splice(start[, deleteCount, elem1, ..., elemN])

const array = [10,20,30,40];

If we want to replace 20 which is at index 1 with 21

arr.splice(1,1,21); //From index 1 replaced with 21 Output : 10,21,30,40

Arrays in JS