Arrays

Array in js

Single variable which can store multiple values. An array is a data structure that allows you to store a collection of elements, such as numbers, strings, objects, or other arrays, in a single variable. Arrays are defined using square brackets [] and each element in the array is separated by a comma.Array index always start from 0.

Code :

const students = ['Harsh','Kashifa','Yogita','Ankita','Vrushali']
console.log(students)

Output :

['Harsh','Kashifa','Yogita','Ankita','Vrushali']

In the above Code we defines an array called students with five elements: Harsh, Kashifa, Yogita, Ankita, and Vrushali.

The console.log() function is then used to print the entire students array to the console.

You can access elements in an array using their index, which starts at 0. For example, to access the first element in students, you would use:

console.log(students[0]);

const students = ['Harsh','Kashifa','Yogita','Ankita','Vrushali']

const lastStudent = students[4]

console.log(lastStudent)

Output :

Vrushali

In the above example we creates an array called students that contains the names of five students: It then creates a constant variable called lastStudent and assigns to it the value of the last element of the students array using the index 4.Finally, the console.log() function is used to output the value of lastStudent to the console.

You can also change the value of an element in an array by assigning a new value to its index, like this:

students[3] = "four";

const students = ['Harsh','Kashifa','Yogita','Ankita','Vrushali']

students[4] = "Vrushali Khedkar"

console.log(students)

Method on Array

1. length

To count total elements in the array

Code :

let marks = [50,45,30,20,10]
marks.length

Output :

5

In the above code we defines an array called marks with five elements: 50, 45, 30, 20, and 10.

The length property of the marks array is then accessed using the . notation and returned. The length property returns the number of elements in the array, which is 5 in this case.

2. push()

To add element from the end of array

Code :

const students = ["A","B","C","D"]
console.log(students)
students.push("E")
console.log(students)

Output :

['A','B','C','D']
['A','B','C','D','E]

In the above code we defines an array called students with four elements: A, B, C, and D.

The first console.log() function is then used to print the entire students array to the console.

The push() method is then called on the students array with the argument E. This adds the string E as a new element at the end of the students array.

The second console.log() function is then used to print the updated students array to the console.

3. pop()

To remove element from the end of array

Code :

const students = ["A","B","C","D"]
console.log(students)
students.pop()
console.log(students)

Output :

['A','B','C','D']
['A','B','C']

In the above code we defines an array called students with four elements: A, B, C, and D.

The first console.log() function is then used to print the entire students array to the console.

The pop() method is then called on the students array. This removes the last element D from the students array.

The second console.log() function is then used to print the updated students array to the console

4. unshift

To insert element from the start of array.

Code :

const students = ["A","B","C","D"]
console.log(students)
students.unshift("E")
console.log(students)

Output :

['A','B','C','D']
['E','A','B','C','D']

In the above code we defines an array called students with four elements: A, B, C, and D.

The first console.log() function is then used to print the entire students array to the console.

The unshift() method is then called on the students array with the argument E. This adds the string E as a new element at the beginning of the students array.

The second console.log() function is then used to print the updated students array to the console.

5. Shift

To delete elements from the start of array.

Code :

const students = ["A","B","C","D"]
console.log(students)
students.shift()
console.log(students)

Output :

['A','B','C','D']
['B','C','D']

In the above code we defines an array called students with four elements: A, B, C, and D.

The first console.log() function is then used to print the entire students array to the console.

The shift() method is then called on the students array. This removes the first element A from the students array.

The second console.log() function is then used to print the updated students array to the console.

6. splice() This function can perform insertion and deletion at once.

splice(index, no.of elements to delete, elements to insert)

Code :

const students = ["A","B","C","D","E","F"]
console.log(students)
students.splice(1, 2,"W","Q")
console.log(students)

Output :

['A','B','C','D','E','F']
['A','B','W','Q',E,'F']

In the above code we can defines an array called students with six elements: A, B, C, D, E, and F.

The first console.log() function is then used to print the entire students array to the console.

The `splice() method is then called on the students array with the arguments 1, 2, W, and Q. This removes two elements starting from the index 1, which removes B and C, and inserts two new elements W and Q in their place.

The second console.log() function is then used to print the updated students array to the console.

7. join()

Convert array to string default separator is , but we can change it.

Code :

const students = ["A","B","C","D","E","F"] <br/>
console.log(students.join())

Output :

['A','B','C','D','E','F']
A,B,C,D,E,F

Code :

const students = ["A","B","C","D","E","F"]
console.log(students.join("*"))

Output :

['A','B','C','D','E','F']
ABCDE*F

8. reverse()

Code :

const arr = ["A","B","C","D"]
arr.reverse()
console.log(arr)

Output :

['D','C','B','A']

9. sort()

Code :

const arr = ["Z","A","D","B"]
arr.sort()
console.log(arr)

Output :

['A','B','D','Z']

10. indexOf()

Code :

const arr = ["Z","A","D","B"]
const index = arr.indexOf("A")
console.log(index)

Output :

1