Arrays Methods

 * push(element) method is used to insert a new element & it will append at the end of the array.

var array = [1,2,3,4];
array.push(5); //array1 = [1,2,3,4,5]
array.push(7); //array1 = [1,2,3,4,5,7]
array.push(2); //array1 = [1,2,3,4,5,7,2]

Time complexity: O(1)

*To delete an element, we will use the pop() method. This will remove from the end. It will return the deleted element.

var array = [1,2,3,4];
array.pop(); //4 array = [1,2,3]
array.pop(); //3 array = [1,2]

Time complexity: O(1)

*Opposite to pop() method is shift(). shift() method will remove elements from the beginning of the array.

var array = [1,2,3,4];
array.shift(); //1 array = [2,3,4]
array.shift(); //2 array = [3,4]

.length property:

If we change the length value then implicitly elements are deleted from the array(from the last).

var array=[3,99,66,55,88];
array.length=2;
console.log('array= '+array); //output:array=[3,99] 

slice(startingIndex, endingIndex):

To return specific elements from an array, we use slice() method.
Here, 
startIndex = will start from "zero"

endIndex = will start from "one"

var array=[3,99,66,55,88];
console.log('array ='+array.slice(1,3)); //output: array=[99,66]

Copying an array: 

There are multiple ways, below are the 2 approaches :

1. By using the "=" operator. Please note, it works as a call by reference. Meaning changing values in one array will reflect in another array as well.

var array1 = [1,2,3,4],
array2 = array1;

array1 // [1,2,3,4]
array2 // [1,2,3,4]

array2[0] = 5;

array1 // [5,2,3,4]
array2 // [5,2,3,4]

2. Using Array.from() Method:

var array1=[3,99,66,55,88];
var array2 = Array.from(array1);
console.log('array2='+array2); //Output: [3,99,66,55,88]

array2[0]=5;
console.log('array1='+array1); //Output: [3,99,66,55,88]
console.log('array2='+array2);//Output: [5,99,66,55,88]