List of Array methods:

• length,
• push,
• slice,
• splice,
• split,
• concat,
• copyWithin,
• includes,
• index of,
• reverse,
• shift,
• unshift,
• sort,

points to be remembered :

Methods that can modify the original array are,

• shift
• unshift
• split
• push
• slice
• splice
• copyWithin

Lenght of Array (arr.length):

The length method in an array is used to calculate the number of elements present inside the array. Syntax:

console.log("name of array".length)

let arr = ["abram", "john", "dustin", "steve", "professor"]
console.log**(arr.length)**;
 Output -> 5

let arr = ["abram", "john", "dustin", "steve", "professor"]
console.log**(arr[1])**;
 Output -> John     (arr[1] -> this denote the 1st index of the error)

let arr = ["abram", "john", "dustin", "steve", "professor"]
console.log**(arr[arr.length -1])**;      (length -1 => 5 - 1 = 4 )  
Output -> professor                      ( index of professor is 4)

To change the values in an Array:

let arr = ["abram", "john", "dustin", "steve", "professor"]
arr[3] = "George"
console.log(arr);
 Output -> In index 3 steve will be replaced by George.

Array Constructors:

Another way to declare an array is Array Constructor, this method is scarcely used by the developer in tech companies.

let newarr = newArr("abram", "john", "dustin", "steve", "professor")

Push:

The push method in the array will modify the original array.

let arr =["abc", "def", "ghi" "jkl"]
console.log**(arr.push("mno"))**  Output -> 5

after pushing "mno" into the array the length will become 5,
if we again 
console.log(arr)  Output -> ['abc', 'def', 'ghi', 'jkl', 'mno']

Slice:

In normal words, slice means cut , like that in the array method slice will the elements in the array.

Syntax:

console.log(arr.slice(start index, endIndex) The endIndex is explicit(not to be counted)

let arr = ["a", "b", "c", "d", "e", "f"]
console.log**(arr.slice(1, 4))**;
 Output -> ['b', 'c', 'd']

Splice:

The splice method is quite similar to the push method. In splice, we can command the values at which index it to insert, it will also overwrite the original array.

Syntax:

console.log(arr.splice(inserting index, Number of items to be removed, value to be added)

let arr = ["a", "b", "c", "d"]
console.log(arr.splice(2, 0, "new value1", "new value2")); 
 Output -> [ ]    it returns like because we didn't delete any element in the array
console.log(arr);
 Output -> ['a', 'b', 'new value 1', 'new value 2', 'c', 'd']

let arr = ["a", "b", "c", "d", "e"]
console.log(arr.splice(2, 2, "new value1", "new value2")); 
 Output -> [ 'c', 'd' ]    the reason for this output is we wrote 2 elements to be removed, so the 'c' & 'd' get removed.
console.log(arr);
 Output ->['a', 'b', 'new value1', new value2', 'e']

Concate:

How to add two arrays in javascript? The answer to this question is Concatenation. By concat method, we are able to add two arrays.

Syntax:

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

let arr   = ["ab", "cd", "ef", "gh"]
let arr1 = [ 1, 2, 3, 4, 5, 6]

console.log(arr.concat(arr1));

let arr   = ["ab", "cd", "ef", "gh"]
let arr1 = [ 1, 2, 3, 4, 5, 6]
let arr2 = [7, 8, 9]

console.log(arr.concat(arr1, arr2))

[ we can also join more than one array at a time using the concat method]

CopyWithin :

The copyWithin() method copies array elements to another position in the array. This method overwrites the existing values.

Syntax:

console.log(arr.copyWithin(startindex,replace value from index, to index))

let arr = [1,2,3,4,5,6,7,8]
console.log(arr.copyWithin(1, 5, 7));
 Output -> [ 1, 6, 7, 4, 5, 6, 7, 8]

Inclues:

This includes work like a boolean whether if the value is present it returns false other than it becomes false.

Syntax:

console.log(arr.inclues(value to be checked, value to be in the index)

let arr = [1, 2, 3, 4, 5, 6, 7]
console.log(arr.includes(5 , 4));
 Output -> true;

let arr = [1, 2, 3, 4, 5, 6, 7]
console.log(arr.includes(5 , 5));
 Output -> false;

Index of:

This method is used to display the index of the element present in the array.

Syntax:

console.log(arr.indexOf(3));

let arr = [ 1, 2, 3, 4, 5]
console.log(arr.indexOf(3))
 Output -> 2

Map:

The method map will be applied to all the elements present in the array. For example, Syntax:

console.log(arr.map(expression));

let arr = [1, 4, 9, 16]
console.log(arr.map(Math.sqrt));
 Output -> [1, 2, 3, 4]     ( Math.sqrt -> this math function is used to find square root of the numbers)

Reverse:

The reverse method will not modify the original array, it will only reverse the array format.

Syntax:

console.log(arr.reverse())

let arr = [ 1, 4, 9, 16 ]
console.log(arr.reverse());

Shift:

This will modify the original array. The shift() method removes the first item of an array.

Syntax:

console.log(arr.shift())

let arr = [1, 4, 9, 16]
console.log(arr.shift());
 Output -> 1     [ the first element in the array gets removed ]
console.log(arr)
 Output -> [ 4, 9, 16 ]

Sort:

The sort() sorts the elements of an array. It will overwrite the original array. It sorts the elements as strings in alphabetical and ascending order.

Syntax: console.log(arr.sort())

let names = ["abram", "paul", "john", "catherine", "michael"]
console.log(names.sort());
 Output -> ['abram', 'catherine', 'john', 'michael', 'paul']

#toString: The toString() method returns a string with array values separated by commas. This method does not change the original array.

Syntax: console.log(arr.toString())

let names = ["abram", "paul", "john", "catherine", "michael"]
console.log(names.toString());
 Output -> abram, paul, john, catherine, michael

unshift:

The unshift() method adds new elements to the beginning of an array. This method overwrites the original array.

let names = ["abram", "paul", "john", "catherine", "michael"]
console.log(names.unshift("steve"));
 Output -> 6
console.log(names);
 Output -> ['steve', 'abram', 'paul', 'john', 'catherine', 'michael']

Split:

The split() method splits a string into an array of substrings. This method returns the new array and it does not change the original string. If (" ") is used as a separator, the string is split between words.

Syntax:

console.log(string.split(separator, limit))

let str = "Javascript";
let ar1 = str.split("a");
console.log(ar1);
 Output -> ['J', 'v', 'script']

let str = "How old are you?";
const myArray = text.split(" ", 3);   [ 3 is the limit of the new array]
 Output -> ['how', 'old', 'are']