push, pop, shift & unshift are the Array Methods which are mostly used while programming in javaScript.
push 
Using push( ) we can add elements to the end of an array.
let arr = [ 1, 2, 3 ];
arr.push(4); // pushing 4 in end of array
console.log(arr); // [ 1, 2, 3, 4 ]
push( ) also returns length of the new array.
let arr = [ 1, 2, 3, 4 ];
let arrLength = arr.push( 5, 6, 7 );
console.log(arrLength); // 7
pop Using pop() Method Remove an element from end of an Array
Pop method remove the last element in an Array.
let arr = [1, 2, 3, 4];
arr.pop(); // will remove last element
console.log(arr); // [ 1, 2, 3 ]
pop() method also returns the removed element.
let arr = [ 1, 2, 3, 4 ];
let removedLastElement = arr.pop();
/*here we have removed last element of array
and stored it in new variable. */
console.log(removedLastElement); // 4
shift Remove an Element from the front of an Array
Shift remove the first element in an Array.
let arr = [ 0, 1, 2, 3 ];
arr.shift();
console.log(arr); // [ 1, 2, 3 ]
shift() also returns the removed element from the array.
let arr = [ 10, 20, 30, 40,50 ];
let removedFirstElement = arr.shift();
console.log(removedFirstElement); // 10
unshift Add elements to the front of an Array
Using unshift() we can add elements to the front of an array.
let arr = [ 1, 2, 3 ];
arr.unshift(0);
console.log(arr); // [ 0, 1, 2, 3 ]
unshift() also returns length of the new array.
let arr = [ 4, 5, 6 ];
let arrLength = arr.unshift( 0, 1, 2, 3 );
console.log(arrLength); // 7
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Ganesh Patil | TA - Edyoda