Array & Methods of Array in JavaScript.

Array :

The Array object uses to store a collection of multiple items under a single variable name. JavaScript arrays are resizable and can contain a mix of different DataType. it is Zero-indexed.

Creating an Array:

• There are two ways to declare an array:

let names = ['Peter','Harry','tony',2,6,true];

(Generally not used in code practices)

let names = new Array('Peter','Harry','tony',2,6,true);

Printing an Array:

console.log(names);
//printing spacific output from index
console.log(names[2]);

Methods of Array in JavaScript:

• Length()

  Use it to get the number of elements in that array.

let names = new Array('Peter','Harry','tony',2,6,true);
console.log(names.length());

output:-6

• Push()

  The push() the method adds one or more elements to the end of an array and returns the new length of the array.

let names = ['Yugal', 'Anurag', 'Surya', 'Anirudh', 'Bipul'];
names.push('VYOM');
console.log(names);

output: [ 'Yugal', 'Anurag', 'Surya', 'Anirudh', 'Bipul', 'VYOM' ]

• Slice()- for printing multiple value

  The slice() method returns a shallow copy of a portion of an array into a new array object selected from start to end (end not included) where start and end represent the index of items in that array. The original array will not be modified.

  let names = ['Yugal', 'Anurag', 'Surya', 'Anirudh', 'Bipul'];
  console.log(names.slice(1, 4));
  

output: [ 'Anurag', 'Surya', 'Anirudh' ]

• splice()

The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

let fruit = ['Apple', 'Bada Apple', 'Chota Apple', 'Double Apple'];
fruit.splice(2, 1, 'Kharab Apple', 'Acha Apple');
console.log(fruit);

In this method, 2 is the index where data puts. 1 is no of elements to be removed it can be 0. and the rest is the data that we want to put.

output:[ 'Apple', 'Bada Apple', 'Kharab Apple', 'Acha Apple', 'Double Apple' ]

• Concatenation

  This method is use to add tow or more arrays.

let arr1 = [1, 2, 3, 4];
let arr2 = [4, 5, 6, 7];
let arr3 = [6, 7, 6, 7,7,7,7,7,7,7,7,7];

console.log(arr1.concat(arr2));
console.log(arr1.concat(arr2, arr3));

output:

[ 1, 2, 3, 4, 4, 5, 6, 7 ]

[ 1, 2, 3, 4, 4, 5, 6, 7, 6, 7, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7 ]

• Fill

  It adds the date to a certain index to end index(exclude) that we need to give , it replaces the date and return the modified array.

  let arr4 = [1, 2, 3, 4, 5, 6, 7, 8, 9];
  arr4.fill('Anurag',2, 4);
  console.log(arr4);
  

output: [1,2,'Anurag','Anurag',4,5,6,7,8,9]

• Includes

  gives output as True or False, The includes() method determines whether an array includes a certain value among its entries.

  let arr = ['yugal','ram','pj','krish'];
  console.log(arr.includes('pj',2);
  

  output: True

• IndexOf

  The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

  let num = [1, 2, 3, 'Anurag', 4, 5, 6, 7, 8, 'Anurag', 'Anurag'];
   console.log(num.indexOf('Anurag'));
  

  Output: 3

  • isArray

    it gives true or False output, it confirms whether a given input is an array or not.

    let num = [1, 2, 3, 'Anurag', 4, 5, 6, 7, 8, 'Anurag', 'Anurag'];
    let num1 = 'Anurag';
    console.log(Array.isArray(num1));
    console.log(Array.isArray(num));
    

> `Output:`
> 
> `False`
> 
> `True`

• join()

  The join() method creates and returns a new string by concatenating all of the elements in an array, separated by commas or a specified separator string. If the array has only one item, then that item will be returned without using the separator.

  let Arr1 = [1, 2, 3, 4, 5, 6, 7];
  let var1 = Arr1.join(' and ');
  console.log(var1);
  

  Output:1 and 2 and 3 and 4 and 5 and 6 and 7

• lastIndexOf

  The lastIndexOf() method returns the last index at which a given element can be found in the array

  let num = [1, 2, 3, 'Anurag', 4, 5, 6, 7, 8, 'Anurag', 'Anurag'];
  console.log(num.indexOf('Anurag'));
  

Output: 3

• (imp) Map()

  this method is applied to each element in the array and it does not change the original array.the results of calling a provided function on every element in the calling array.

  let num = [1,2,3,4,5];
  console.log(num.map(Math.sqrt));
  

  Output: [1,4,9,16,25]

• Pop()

  The pop() method removes the last element from an array and returns that element. This method changes the length of the array.

   let maths = [1, 4, 9, 16, 25];
  console.log(maths.pop());
  console.log(maths)
  

  Output: 25

  [1,4,9,16]

• Reverse

  elements order in the array will be turned towards the direction opposite to that previously stated.

  let num = ['one','two','three','four'];
  console.log(num.reverse());
  

  Output: ['Four ','three','two',one']

• shift

  The shift() method removes the first element from an array and returns that removed element. This method changes the length of the array.

  let num = [1,2,3,4,5]
  console.log(num.shift());
  console.log(num);
  

  Output: 1

  [2,3,4,5]

• sort

  It sorts the element and changes the order of elements into ascending order.

  let num = ['Surya', 'Anirudh', 'Bipul'];
  console.log(num.sort());
  
  const array1 = [1, 30, 4, 21, 100000];
  array1.sort();
  console.log(array1);
  

  Output: [Anirudh','Bipul','Surya']

  [1, 100000, 21, 30, 4]

• unshift

  The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.

  let fruit = ['Apple', 'Bada Apple', 'Chota Apple', 'Double Apple'];
  
   fruit.unshift('Apple 1', 'Grapes 2');
   console.log(fruit);
  

  ['Apple 1', 'Grapes 2', 'Apple', 'Bada Apple', 'Chota Apple', 'Double Apple' ]

• Converting to Array

  convert any element(String) into array

  let name= 'Yugal';
  let arr = name.split('');
  console.log(arr);
  

  Output: ['Y', 'u',' g',' a','l']

• (imp) for of

  The forEach() method executes a provided function once for each array element.

  let fruit = ['Apple', 'Bada Apple', 'Chota Apple', 'Double Apple'];
  let Upperfruit = []; // empty Array
  
  for (let name of fruit) {
      Upperfruit.push(name.toUpperCase());
  }
  console.log(Upperfruit);
  

  Output:

  [ 'APPLE', 'BADA APPLE', 'CHOTA APPLE', 'DOUBLE APPLE' ]

• Key

  The keys() method returns a new Array Iterator object that contains the keys for each index in the array.

  const array1 = ['a', 'b', 'c'];
  const iterator = array1.keys();
  
  for (const key of iterator) {
    console.log(key);
  }
  

Output: 0

1

2

Hope get the idea about the Array of the JavaScript .

thank You !