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Arrays in Javascript

Arrays in Javascript

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Devananth A
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Welcome back developers , If you are someone who just started programming then this is a must read blog for you.

In this blog , we will be covering Arrays.

What is an Array ?

Array is a datastructure which is used to store multiple values in a single variable. (i.e : we can store more than one value at a time)

Consider a case , where you are supposed get all students name of a department. In this case you can't create a separate variable for storing each student name.

But what if you can create a variable of dept_name and have all the students name belonging to that department. Sounds cool right , this is the concept of arrays.

Syntax

//Declaring an array
const array_name = [ ];

//Declaring an array with values
const array_name = [ value1 , value2 , ... ];

Eg :

 //Declaring an array or Creating an empty array
 const arr = [];

 //Creating an array with values
 const numbers = [ 1 , 2 , 3 , 4 , 5];

 //Creating array for storing students name of CSE Department
 const cse = ["Akash" , "Arjunan" , "Deeraj" , "Arun" , "Anandh"];

Unlike C , C++ languages Javascript arrays can store values of different datatypes in a single array.

 const mixDatatypes = [ "String" , 3 , 4.00 ];

Accessing the array elements

The values of a array can be accessed using index. The index of an array starts from 0 to length of the array - 1.

ie: If you wanna access the first element of the array , then you need to mention the index value as 0

Syntax

array_name[index] 

 const arr = [ 1 , 2 , 3 , 4 , 5];

                 output
  arr[0]    =>     1 
  arr[4]    =>     5

If you use a invalid index it would return undefined.

What if you do know the size of the array ?

Array has a property which would return the length of the array

ie. array_name.length

  arr.length => 5

Methods

1. push

This method is used to add elements into the array . It adds the elements at the end of the array.

  const arr = []

  for(var i = 1 ; i<=5 ; i++)
        arr.push(i);

  console.log(arr);  // [ 1 , 2 , 3 , 4 , 5 ]

2. pop

This method is used to remove elements from the end of the array.

    arr.pop();   // 5 is removed

    console.log(arr);  // [ 1 , 2 , 3 , 4 ]

3. unshift

This method is used to add elements in the beginning of the array.

 arr.unshift(0);

 console.log(arr); //[0 , 1 , 2 , 3 , 4 ]

4. shift

This is method is used to remove element from the beginning of the array.

  arr.shift();   // 0 is removed

  console.log(arr); //[ 1 , 2 , 3 , 4 ]

5. indexOf

This method returns the index(ie.position of the element) of element in the array. When there are duplicates it would return the first occuring index.

  console.log(arr.indexOf(2));   // 1 ( remember array index starts from 0 )

6. splice

This method takes two arguments one is pos (ie.position of the element to be removed) and other is noOfElements from that position to be removed;

array_name.splice(pos , n);

arr.splice(2,2);

console.log(arr);  // [ 1 , 2]

These are the basic array methods that are frequently used in programming.

If you wanna learn more about array methods , check this out : developer.mozilla.org/en-US/docs/Web/JavaSc..

JavaScript