In this Lecture, we going to study the JavaScript Array

we going to cover the following topics in this lecture: -

1. what is array

2. push

3. pop

4. shift

5. unshift

6. slice

7. splice

8. concertation

9. fill

10. include

11. index of

12. isArray

13. join

14. lastIndexOf

15. map

16. reverse

17. sort

18. for of

What is Array: -

The array is a memory that store all element sequentially. It starts from 0 to its element length.

Let arr= [1,2,3,6,8]

Let is a data type

arr is a variable name (it can be any name you want)

[1,2, 3,6,8] it means there are 5 elements present in an array

Array lenght

let names=['ayear','babita ji','jetalal','abdul','sundar'];


//lenght of array***********
console.log(names.length);

Output: - 5

As we discuss Array start from the 0th position so how the output is 5 but in the array.length count starts from 1th position to array length.

Push: -

It is used to add an element in the array from the last position.

let names= ['ayear','babita ji','jetalal','abdul','sundar'];
//push*********

names.push('sodi_paji');
console.log(names);

Output: -

[ 'ayear', 'babita ji', 'jetalal', 'abdul', 'sundar', 'sodi_paji' ]

POP: -

let names= ['ayear','babita ji','jetalal','abdul','sundar'];
names.pop();
console.log(names);

Output: -
[ 'ayear', 'babita ji', 'jetalal', 'abdul' ]

Shift: -

The shift() Method is used to remove the first element from array.

const fruits=['Apple','banana','grapes'];
fruits.shift();
console.log(fruits);

ouutput:- ['banana','grapes']

Unshift: -

The unshift() Method is used to add a new element from the beginning of an array.

const fruits=['Apple','banana','grapes']
fruits.unshift['Mango','Patato'];
console.log(fruits)

output: -['Mango','Patato','Apple','banana','grapes']

Slice: -

It is used to remove the element from the array but requires its index value.

slice does not alter the original array

Slice(a,b)

a is an index of the array.

b is also an index but it excludes the b index element in the slice.

let names= ['ayear','babita ji','jetalal','abdul','sundar'];
console.log(names.slice(1,3));
console.log(names. Slice(0));

Output: -
[ 'babita ji', 'jetalal' ]
[ 'ayear', 'babita ji', 'jetalal', 'abdul', 'sundar' ]

Splice: -

The splice method is used to add or remove an element from an array.

But Splice do change in the orignal array

let fruit=['apple','bada apple','chota apple','double apple'];
fruit.splice(2,1,'kharab apple','acha aaple');
console.log(fruit);

fruit.splice(1,0,'add any item');
console.log(fruit);

let users=['TOM','TIM','TON','SAM','SOR','SOD'];
users.splice(1,3,'CHETAK');
console.log(users);

Output: -

[ 'apple', 'bada apple', 'kharab apple', 'acha aaple', 'double apple' ]
[
  'apple',
  'add any item',
  'bada apple',
  'kharab apple',
  'acha aaple',
  'double apple'
]
[ 'TOM', 'CHETAK', 'SOR', 'SOD' ]

concertation: -

It use to add the string as well as the array

let arr1=[1,2,3,4];
let arr2=[5,6,7,8];

const arr3=arr1.concat(arr2);
console.log(arr3);

let arr4=[11,12,13,14];
let arr5=[15,16,17,18];
let arr6=[19,20];
console.log(arr4.concat(arr5,arr6,arr2));

Output: -
[
  1, 2, 3, 4,
  5, 6, 7, 8
]
[
  11, 12, 13, 14, 15, 16,
  17, 18, 19, 20,  5,  6,
   7,  8
]

include: -

include () method is used to check whether the element is present in the array or not

include()method return true or false

include(element,index of element)

let arr1=[1,12,38,40];
console.log(arr1.include(12,2));
Output: -true

let arr=[1,2,3,4,5,6];
console.log(arr.includes(3,2));        output: - true
console.log(arr.includes(3,4));        output: - false

IndexOf(): -

It is used to find the index of array element

let arr=[1,2,3,4,5,6,'Ashu','abhay'];
console.log(arr.indexOf(3));
console.log(arr.indexOf('Ashu'));

Output: -

2

6

isArray: -

It is used to identify the weather the input is array or not return "true" and "false".

let arr=[1,2,3,4,5,6,'Ashu','abhay'];
console.log(Array.isArray(arr))

let check='it is array or sting';
console.log(Array.isArray(check));
console.log(typeof(check));

Output: - true

false

Join(): -

The join() method returns an array as a string.

The join() method does not change the original array.

Any separator can be specified. The default is comma (,).

let arr=[1,2,3,4,5,6,'Ashu','abhay'];

console.log(arr.join());


console.log(arr.join(' + '));

let check=arr.join(' * ');
console.log(check);
console.log(typeof(check));

Output: -

1,2,3,4,5,6,Ashu,abhay
1 + 2 + 3 + 4 + 5 + 6 + Ashu + abhay
1 * 2 * 3 * 4 * 5 * 6 * Ashu * Abhay
string

last Index of: -

It will return the last index of element from array

 let arr=[1,2,3,'Ashu',5,'Ashu',6,'Ashu'];
 console.log(arr.lastIndexOf('Ashu'));

Output: -

7

NOTE : - REST TOPICES WE GOING TO STUDY IN PART 02