For JavaScript Theorytical questions: "https://github.com/sudheerj/javascript-interview-questions"

For Reactjs theory questions: https://github.com/sudheerj/reactjs-interview-questions/tree/master/.github/workflows

For Google, Facebook, Microsoft coding challenges: https://youtube.com/c/KevinNaughtonJr

Jest: https://github.com/sapegin/jest-cheat-sheet

https://plainenglish.io/blog/50-javascript-output-questions

https://github.com/priya42bagde/javascript-interview-questions?organization=priya42bagde&organization=priya42bagde#what-is-json-and-its-common-operations ---> IMP

https://learnersbucket.com/javascript-sde-cheat-sheet/

https://javascript.info/

https://frontenddeveloperinterview.netlify.app/

================================================================================================================================================================================

Code 1: Remove Duplicate characters from String

function removeDuplicateCharacters() {

var string='priya riya supriya'

let result= string.split('').filter((item, index, arr)=> {

return arr.indexOf(item) == index;

}).join('');

return result;

}

console.log(removeDuplicateCharacters());

================================================================================================================================================================================

Code 2: Remove Duplicate characters from array of element and find the count of an elements using set object

var arr = [55, 44, 55,67,67,67,67,8,8,8,8,8,65,1,2,3,3,34,5];

var unique = [...new Set(arr)]

console.log(unique) //output: [55, 44, 67, 8, 65, 1, 2, 3, 34, 5]

console.log(unique.length) //output: 10

================================================================================================================================================================================

Code 3: Remove Duplicate characters from array of element using filter

var myArray = ['a', 1, 'a', 2, '1'];

var unique = myArray.filter((value, index, arr) => arr.indexOf(value) === index);

================================================================================================================================================================================

Code 4:String reverse without reversing of individual words (Array of elements can be reverse with reverse() method but for string it is won't possible so required to split

and then join().

function removeDuplicates(){

var string ="India is my country"

let result = string.split('').reverse().join('').split(' ').reverse().join(' ')

return result

}

console.log(removeDuplicates())

output = "aidnI si ym yrtnuoc"

------------------------------------------

var reverseWords = function(s) {

let res = '';

let word = '';

for (let c of s) {

if (c === ' ') {

res += word + c;

word = '';

} else {

word = c + word;

}

}

return res + word;

};

console.log(reverseWords("priya bagde"))

================================================================================================================================================================================

Code 5:String reverse with reversing of individual words

function withoutReverse(){

var string ="India is my country"

let result = string.split('').reverse().join('')

return result

}

console.log(withoutReverse())

output = "yrtnuoc ym si aidnI"

================================================================================================================================================================================

Code 6:String reverse without using inbult function

function Reverse(){

var string ="India is my country";

var result="";

for( var i=string.length-1; i>=0 ; i-- ) {

result=result+string[i] }

return result

}

console.log(Reverse())

output = "yrtnuoc ym si aidnI"

================================================================================================================================================================================

Code 7: Find factorial of user input number

const number = parseInt(prompt('Enter a positive integer: '));

if (number < 0) { console.log('Error! Factorial for negative number does not exist.')}

else if (number === 0) { console.log(`The factorial is 1.`)}

else {

let fact = 1;

for (i = 1; i <= number; i++) {

fact *= i;

}

console.log(`The factorial is ${fact}.`);

}

================================================================================================================================================================================

Code 8:Anagram

function checkStringsAnagram() {

var a="Army";

var b="Mary"

let str1 = a.toLowerCase().split('').sort().join('');

let str2 = b.toLowerCase().split('').sort().join('');

if(str1 === str2){

console.log("True");

}

else {

console.log("False");

}

}

================================================================================================================================================================================

Code 9: Swapping of 2 numbers with third variable

let a=10;

let b=20;

let c;

c=a;

a=b;

b=c;

console.log (a,b,c)

================================================================================================================================================================================

Code 10: Swapping of 2 numbers without third variable

let a=10;

let b=20;

a=a+b //30

b=a-b //10

a=a-b //20

console.log (a,b)

================================================================================================================================================================================

Code 11: To check the string or number is palindrome or not( ex: 121,madam,anna) using reverse method

function checkPalindrome(){

const string = "anmna"

let arr= string.split('').reverse().join('')

//console.log(arr)

if (string==arr){

console.log("Palindrome")

}

else{

console.log("Not Palindrome")

}

}

checkPalindrome()

================================================================================================================================================================================

Code 12: To check the string or number is palindrome or not( ex: 121,madam,anna) using diving length by 2 and then comparing

function checkPalindrome(){

const string = "12321"

let len = string.length;

for (i=0; i<len/2;i++){

if (string[i]!==string[len-1-i]){

console.log("Not Palindrome")

}

else{

console.log(" Palindrome")

}

}

}

checkPalindrome()

================================================================================================================================================================================

Code 13: To find longest word from a string using (for of) /*for(var i=0; i>=num; i++) means iterate by indexing*/ /*for (var word of words) means iterate by an elements not

by indexing*/

function longestWord(){

let string = "supriya is a masooooom good girl"

var words= string.split(' ')

var longest=" "

for(var word of words){

console.log(word)

if (word.length > longest.length)

{

longest=word;

}

}

return longest.length

}

longestWord()

---------------------------

function longestWord(){

let string = "supriya is a hahahahaha good girl"

var arr= string.split(' ')

var longest=" "

for(var i=0; i<arr.length; i++){

if (arr[i].length > longest.length)

{

longest=arr[i];

}

}

return longest

}

console.log(longestWord())

================================================================================================================================================================================

Code 14: To find longest word from a string using functions

function findLongestWord() {

var str = "Priya is a goog girl and having hardworking skill"

var longestWord = str.split(' ').sort((a, b) => {return b.length - a.length }); //in desc order //from greater to smallest word

console.log(longestWord[0]);

console.log(longestWord[0].length);

}

findLongestWord();

================================================================================================================================================================================

Code 15: To find longest word from a string using custom code

function longest() {

var str ="Priya is a good girl and having hardworking skills"

var words = str.split(' ');

var longest = '';

for (var i = 0; i < words.length; i++) {

if (words[i].length > longest.length) {

longest = words[i];

}

}

console.log(longest)

return longest;

}

longest();

================================================================================================================================================================================

Code 16: To find longest common string from array of strings

function longestCommonString(){

array=["go","google","gosh"]

var arr = array.sort()

var i=0;

while(arr[0].length>0 && arr[0].charAt(i)===arr[arr.length-1].charAt(i)){

i++;

}

console.log(arr[0].substring(0,i)) // "go"

return arr[0].substring(0,i)

}

longestCommonString()

--------------------------------------------------------------------

function longestCommonString(){

array=["got","google","gosh"]

var arr = array.sort()

var i=0;

while(arr[0].length>0 && arr[0][i]===arr[arr.length-1][i]){

i++;

}

console.log(arr[0].slice(0,i))

}

longestCommonString()

--------------------------------------------------------------------

function longestCommonString(){

let array=["go","google","gosh"]

var arr = array.sort((a,b)=>a.length-b.length)

let result =""

for(let i=0; i<arr[0].length; i++){

if(arr[0][i]===arr[arr.length-1][i]){

result+=arr[0][i]

}

}

return result

}

console.log(longestCommonString())

================================================================================================================================================================================

Code 17: To find vowels and its count in a given string

function vowelCounts(){

vowels=["a","i","e","o","u"]

var str ="priya"

count=0;

for(var letter of str.toLowerCase())

{

if(vowels.includes(letter))

{

count++;

console.log(letter)

}

}

console.log(count)

return count

}

vowelCounts()

================================================================================================================================================================================

Code 18:To find character occurance fro the string

function characterOccurance(str,letter){

let count =0;

for(var i=0; i<str.length-1; i++){

if(str.charAt(i)===letter)

{

count++

}

}

console.log(count)

return count

}

characterOccurance("priyapri", "p")

================================================================================================================================================================================

Code 19: To find a first pair whose sum is zero

function getSumPairZero(array)

{

for(let number of array)

{

for(let i=1; i<array.length; i++)

{

if(number+array[i]===0)

{

return [number, array[i]]

}

}

}

}

const result = getSumPairZero([-5,-4,-3,-2,-1,0,1,2,3,4,5])

console.log(result)

------------------------------------------------

function getSumPairZero(array)

{

for(let j=0; j<array.length;j++)

{

for(let i=1; i<array.length; i++)

{

if(array[j]+array[i]===0)

{

return [array[j], array[i]]

}

}

}

}

const result = getSumPairZero([-5,-4,-3,-2,-1,0,1,2,3,4,5])

console.log(result)

================================================================================================================================================================================

Code 20: To find a first pair whose sum is zero using indexing //Firstly do a sort here

function getSumPairZero(array)

{

let left = 0;

let right = array.length-1;

while(left<right)

{

sum = array[left]+array[right]

if(sum===0){

return [array[left],array[right]]

}else if(sum>0){

right--;

}else{

left++;

}

}

}

const result = getSumPairZero([-5,-4,-3,-2,-1,0,2,4,6,8])

console.log(result)

================================================================================================================================================================================

Code 21: To find the largest pair of the 2 elements using indexing with unsorted elements

function largestPairSumofTwo(numbers){

const num = numbers.sort((a, b) => b - a);

console.log(num)

return num[0] + num[1];

}

const result = largestPairSumofTwo([9,7,8,4,5,6,1,2,3])

console.log(result)

================================================================================================================================================================================

Code 22: To find the largest pair of the 2 elements using indexing with sorted elements

function largestPairSumofTwo(num){

return num[num.length-1] + num[num.length-2];

}

const result = largestPairSumofTwo([1,2,3,4,5,6,7,8,9])

console.log(result)

================================================================================================================================================================================

Code 23: To find the index of an element from an array

const letters = ['a', 'b', 'c']

const index = letters.indexOf('b')

console.log(index) // `1`

================================================================================================================================================================================

Code 24: Fibonacci Series (0,1,1,2,3,5,8,13....)

function fibonacciSeries(){

const number = parseInt(prompt('Enter the number of terms: '));

let n1 = 0, n2 = 1, nextTerm, arr=[]

arr.push(n1)

arr.push(n2)

for (let i = 1; i <= number; i++)

{

console.log(n1);

nextTerm = n1 + n2;

n1 = n2;

n2 = nextTerm;

arr.push(nextTerm)

}

return arr

}

console.log(fibonacciSeries())

================================================================================================================================================================================

Code 25: Fibonacci Series (0,1,1,2,3,5,8,13....) where keeping in array

function listFibonacci(n) {

var arr = [0, 1]

for (var i = 1; i < n; i++)

arr.push(arr[i] + arr[i - 1])

return arr

}

console.log(listFibonacci(4))

-----------------------------------------------------------------------

function listFibonacci(n) {

var arr = [0, 1]

for (var i = 0; i < n; i++)

arr.push(arr[i] + arr[i + 1])

return arr

}

console.log(listFibonacci(4))

================================================================================================================================================================================

Code 26: Finding a missing elements in an array and then add with existing elements. (-1 means if elements not found then it will return always -1 as per rule)

function missingElement(){

var a = [1,2,5]

var missing = [];

for (var i = 1; i <= 6; i++)

{

if (a.indexOf(i) == -1)

{

missing.push(i);

}

}

console.log(missing) //missing array

console.log(a.concat(missing).sort()); //actual+missing elements

}

missingElement()

================================================================================================================================================================================

Code 27: Find the missing no. in an array

function missing(arr) {

var x = 0;

for (var i = 0; i < arr.length; i++) {

x = x + 1;

if (arr[i] != x) {

return(x); //9

}

}

}

missing([1, 2, 3, 4, 5, 6, 7, 8, 10])

-------------------------------------------

function missing(arr) {

for (var i = 0, x=1; i < arr.length; x++,i++) {

if (arr[i] != x) { //index value comparing with pointer

return x; //9

}

}

}

console.log(missing([1, 2, 3, 4, 5, 6, 7, 8, 10]))

================================================================================================================================================================================

Code 28: Sorting of an string/character

function sorting(arr) {

return arr.sort()

}

console.log(sorting(["d","g","y","e","r","p"]))

================================================================================================================================================================================

Code 29: Sorting of an number

function sorting(arr) {

return arr.sort((a,b)=>{return a-b})

}

console.log(sorting([1,23,34,2,76,78])) //[1, 2, 23, 34, 76, 78]

================================================================================================================================================================================

Code 30: To check if given number is prime or not

function isPrime(num) {

if(num < 2) return false;

for (let k = 2; k < num; k++){

if( num % k == 0){ return false}

}

return true;

}

console.log(isPrime(17)) //true

================================================================================================================================================================================

Code 31: To print all the numbers from 2 to 100

for (let i = 2; i <= 100; i++) {

let flag = 0;

for (let j = 2; j < i; j++) {

if (i % j == 0) {

flag = 1;

break;

}

}

if (i > 1 && flag == 0) {

console.log(i);

}

}

--------------------------------------

for (let i = 2; i <= 100; i++)

{

let flag = 0;

for (let j = 2; j < i; j++) { //2<2 //2<3 //3<4

if (i % j == 0) {

flag = 1;

break;

}

}

if (i > 1 && flag == 0)

{

document.write(i+ "</br>");

}

}

================================================================================================================================================================================

Code 32: To find unique values from 2 arrays and keep into one array.

function uniqueElements(arr1,arr2){

let arr =[...arr1,...arr2];

let array =[...new Set(arr)]

console.log(array)

}

uniqueElements([1,2,3,4,4],[2,3,4,5,6])

================================================================================================================================================================================

Code 33: Find first duplicate element from an array

function firstDuplicate() {

let arr = [1,2,2,5,5];

let data = {};

for (var item of arr) {

if (data[item]) {

return item

} else {

data[item] = item

console.log(data[item])

}

}

return -1

}

console.log(firstDuplicate())

================================================================================================================================================================================

Code 34: Write a program that prints the numbers from 1 to 100. But for multiples of three, print "Fizz" instead of the number, and for the multiples of five, print "Buzz".

For numbers which are multiples of both three and five, print "FizzBuzz"

for (var i=1; i <= 20; i++)

{

if (i % 15 == 0)

console.log("FizzBuzz");

else if (i % 3 == 0)

console.log("Fizz");

else if (i % 5 == 0)

console.log("Buzz");

else

console.log(i);

}

================================================================================================================================================================================

Code 35: Uppercase of each first letter of a words

function upperCaseFirsstLetter(){

var string ="India is my country";

var words = string.toLowerCase().split(" ")

for( var i=0; i<words.length; i++) {

words[i]=words[i][0].toUpperCase() + words[i].slice(1) //slice is used here to give all the letters except first letter.

}

return words.join(" ")

}

console.log(upperCaseFirsstLetter())

================================================================================================================================================================================

Code 36: Uppercase of each first letter of a words using map function

function upperCaseFirsstLetter(){

var string ="India is my country";

var words = string.toLowerCase().split(" ").map((ele)=>{

return ele[0].toUpperCase() + ele.slice(1)

})

return words.join(" ")

}

console.log(upperCaseFirsstLetter())

================================================================================================================================================================================

Code 37: To check ending of the string with given character/s using inbuild function

function confirmEnding(str,target){

return str.endsWith(target) //true

}

console.log(confirmEnding("priya","a"))

===============================================================================================================================================================================

Code 38: To check ending of the string with given character/s using custom

function confirmEnding(str,target){

return str.substr(-target.length)===target

}

console.log(confirmEnding("priya","a"))

===============================================================================================================================================================================

Code 39: To find the largest elements fro the 2 dimensional array

function largestFromArray(arr){

var max=[];

for(var i=0; i<arr.length;i++){

var tempMax =arr[i][0] //first elements of the 4 internal arrays i,e(1,5,45,89

for(var j=0; j<arr[i].length; j++){

var currElement = arr[i][j];

if(currElement>=tempMax){

tempMax = currElement

}

}

max.push(tempMax)

}

console.log(max)

return max;

}

largestFromArray([[1,2,3,4],[5,6,7,9],[45,76,2,1],[89,90,87,9]])

================================================================================================================================================================================

Code 40: To find the largest elements fro the 2 dimensional array in another way

function largestFromArray(arr){

var max=[0,0,0,0];

for(var i=0; i<arr.length;i++){

for(var j=0; j<arr[i].length; j++)

{

if(arr[i][j]>=max[i]){

max[i] = arr[i][j]

}

}

}

console.log(max)

return max;

}

largestFromArray([[1,2,3,4],[5,6,7,9],[45,76,2,1],[89,90,87,9]])

================================================================================================================================================================================

Code 41: Print string n times using inbuilt function

function repeatStrinNumTimes(str, num){

if (num<1) return ""

return str.repeat(num)

}

console.log(repeatStrinNumTimes("priya",3))

================================================================================================================================================================================

Code 42: Print string n times in custom way

function repeatStrinNumTimes(str, num){

var final="";

if(num<0) return ""

for(var i=0; i<num;i++)

{

final=final+str

}

return final

}

console.log(repeatStrinNumTimes("priya",3))

================================================================================================================================================================================

Code 43:Print string n times in custom way

function repeatStrinNumTimes(str, num){

if(num<0) return ""

if(num===1) return str

return str+ repeatStrinNumTimes(str, num-1)

}

console.log(repeatStrinNumTimes("priya",3))

================================================================================================================================================================================

Code 44: Truncate the string

function truncateString(str, num){

if(num<=3) return str.slice(0,num)

return str.slice(0,num-3)+"..." //retuen only 4 digits thats why subtracted from 3

}

console.log(truncateString("priyabagde",2)) //pr

console.log(truncateString("priyabagde",4)) //p... //retuen only 4 digits

================================================================================================================================================================================

Code 45: Converting one dimensional array into n dimensional array using slice

function chunkArrayInGroup(arr, size){

var group=[]

while(arr.length>0){

group.push(arr.slice(0, size))

arr = arr.slice(size)

}

return group

}

console.log (chunkArrayInGroup(['a','b','c','d'],2)) //[["a", "b"], ["c", "d"]]

================================================================================================================================================================================

Code 46: Converting one dimensional array into n dimensional array using splice

function chunkArrayInGroup(arr, size){

var group=[]

while(arr.length>0){

group.push(arr.splice(0, size))

}

return group

}

console.log (chunkArrayInGroup(['a','b','c','d'],2)) //[["a", "b"], ["c", "d"]]

================================================================================================================================================================================

Code 47: To find only truthy values

function removeFalseValue(arr){

var trueth = []

for (var item of arr){

if(item){

trueth.push(item)

}

}

return trueth

}

console.log(removeFalseValue(["priya", 0 ,"", false, null,undefined, "ate", Nan ,9 ])) //["priya","ate",9]

================================================================================================================================================================================

Code 49: To find only truthy values using filter

function removeFalseValue(arr){

return arr.filter((item)=>{

return item})

}

console.log(removeFalseValue(["priya", 0 ,"", false, null,undefined, "ate", 9 ]))

================================================================================================================================================================================

Code 50: Checking all letters of second words should present in first word, in the same order using include function

function characterPresent(arr){

var first = arr[0].toLowerCase()

var second = arr[1].toLowerCase()

for (var letter of second){

if(!first.includes(letter)){

return false

}

}

return true

}

console.log(characterPresent(["hello","hey"]))

================================================================================================================================================================================

Code 51: Checking all letters of second words should present in first word, in the same order using indexOf without indexing i.e for-of loop

function characterPresent(arr){

var first = arr[0].toLowerCase()

var second = arr[1].toLowerCase()

for (var letter of second){

if(first.indexOf(letter)== -1){ //-1 means not found in array

return false

}

}

return true

}

console.log(characterPresent(["hello","he"]))

---------------------------------------------------

function characterPresent(arr){

var first = arr[0].toLowerCase()

var second = arr[1].toLowerCase()

for (var i=0; i<second.length; i++){

if(!first.includes(second[i])){ //-1 means not found in array

return false

}

}

return true

}

console.log(characterPresent(["hello","he"]))

================================================================================================================================================================================

Code 52: Checking all letters of second words should present in first word, in the same order using indexOf with indexing

function characterPresent(arr){

var first = arr[0].toLowerCase()

var second = arr[1].toLowerCase()

for (var i=0; i<second.length; i++){

if(first.indexOf(second)== -1){ //-1 means not found in array

return false

}

}

return true

}

console.log(characterPresent(["hello","he"]))

================================================================================================================================================================================

Code 53: Unique values only from 2 arrays

function diffArrayElement(arr1, arr2){

var result =[]

for(var i=0; i<arr1.length; i++){

if(arr2.indexOf(arr1[i]) === -1){

result.push(arr1[i])

}

}

for(var j=0; j<arr2.length; j++){

if(arr1.indexOf(arr2[j]) === -1){

result.push(arr2[j])

}

}

return result

}

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

================================================================================================================================================================================

Code 54: Unique values only from 2 arrays

function diffArrayElement(arr1, arr2){

var combine = arr1.concat(arr2)

return combine.filter( (num)=>{

if(arr1.indexOf(num)== -1 || arr2.indexOf(num)== -1 ) return num

})

}

console.log(diffArrayElement([1,2,3,4], [2,3,4,5])) [1,5]

================================================================================================================================================================================

Code 55: Remove Duplicates from 2 arrays using Set

function uniquefromArrays(arr1, arr2){

let arr = [...arr1, ...arr2]

let unique = [...new Set(arr)];

return unique

}

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

================================================================================================================================================================================

code 56: Sum of all numbers from start to end given number

function sumFromStartToEnd(arr){

var start = Math.min(arr[0], arr[1])

var end = Math.max(arr[0], arr[1])

sum =0

for(var i= start; i<=end; i++){

sum+=i

}

return sum

}

console.log(sumFromStartToEnd([1,4]))

================================================================================================================================================================================

code 57: Remove or Delete elements from an array using various ways

Way 1: Removing Elements from End of a JavaScript Array

var ar = [1, 2, 3, 4, 5, 6];

ar.length = 4; // set length to remove elements

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

Way 2: Removing Elements from Beginning of a JavaScript Array

var ar = ['zero', 'one', 'two', 'three'];

ar.shift(); // returns "zero"

console.log( ar ); // ["one", "two", "three"]

Way 3: Using Splice to Remove Array Elements in JavaScript

var list = ["bar", "baz", "foo", "qux"];

list.splice(0, 2); // Starting at index position 0, remove two elements ["bar", "baz"] and retains ["foo", "qux"].

Way 4: Removing Array Items By Value Using Splice

var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];

for( var i = 0; i < arr.length; i++){

if ( arr[i] === 5) {

arr.splice(i, 1);

}

} // [1, 2, 3, 4, 6, 7, 8, 9, 0]

OR

var arr = [1, 2, 3, 4, 5, 5, 6, 7, 8, 5, 9, 0];

for( var i = 0; i < arr.length; i++){

if ( arr[i] === 5) {

arr.splice(i, 1);

i--;

}

} // [1, 2, 3, 4, 6, 7, 8, 9, 0]

Way 5: Using the Array filter Method to Remove Items By Value

var array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];

var filtered = array.filter(function(value, index, arr){

return value > 5;

}); //filtered => [6, 7, 8, 9]

Way 6: Making a Remove Method

function arrayRemove(arr, value) {

return arr.filter(function(ele){

return ele != value;

});

}

var result = arrayRemove(array, 6); // result = [1, 2, 3, 4, 5, 7, 8, 9, 0]

Way 7: Explicitly Remove Array Elements Using the Delete Operator

var ar = [1, 2, 3, 4, 5, 6];

delete ar[4]; // delete element with index 4

console.log( ar ); // [1, 2, 3, 4, undefined, 6]

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Code 58 : Spiral Matrix Printing | Print the elements of a matrix in spiral form

var input = [[1, 2, 3, 4],

[5, 6, 7, 8],

[9, 10, 11, 12],

[13, 14, 15, 16]];

function run(input, result) {

// add the first row to result

result = result.concat(input.shift());

console.log("res1", result) //[1, 2, 3, 4] //[1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7]

console.log("in1", input) //[[5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]] // [[10, 11]]

// add the last element of each remaining row

input.forEach(function(rightEnd) {

result.push(rightEnd.pop());

});

console.log("res2", result) //[1, 2, 3, 4, 8, 12, 16] //[1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11]

console.log("in2", input) //[[5, 6, 7], [9, 10, 11], [13, 14, 15]] // [[10]]

// add the last row in reverse order

result = result.concat(input.pop().reverse());

console.log("res3", result) //[1, 2, 3, 4, 8, 12, 16, 15, 14, 13] //[1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10]

console.log("in3", input) //[[5, 6, 7], [9, 10, 11]]

// add the first element in each remaining row (going upwards)

var tmp = [];

input.forEach(function(leftEnd) {

tmp.push(leftEnd.shift());

});

console.log("res4", result) //[1, 2, 3, 4, 8, 12, 16, 15, 14, 13]

console.log("in4", input) //[[6, 7], [10, 11]]

result = result.concat(tmp.reverse());

console.log("temp", temp) //[9, 5]

console.log("res5", result) //[1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5]

console.log("in5", input) //[[6, 7], [10, 11]]

//again start the function

return run(input, result);

}

console.log('result', run(input, [])); // [1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10]

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Code 59: Currying function i.e sum of multiple argument functions //inner function can access outer function variables but outer functions can't able to acceess inner function.

function sum(a){

return function sum(b){

return function sum(c){

return function sum(d){

return a+b+c+d;

}

}

}

}

console.log(sum(1)(2)(3)(4))

OR

const sum = (a) => (b) => (c) => (d) => a+b+c+d // using ES6

console.log(sum(1)(2)(3)(4))

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Code 60: Find SUM, PRODUCT AND AVERAGE of the numbers //accumulation means collection

let arr=[1,2,3,4,5]

let sum = arr.reduce((accum, curr) =>{

return accum + curr;

})

console.log(sum) //15

OR

let sum = arr.reduce((accum, curr) =>{

return accum + curr;

},5) // can set initial value as 5 also

console.log(sum) //20

let product = arr.reduce((accum, curr) =>{

return accum * curr;

})

console.log(product)//120

let average = arr.reduce((accum, curr, index, array) =>{

let total = accum + curr;

if(index === array.length-1){

return total/array.length

}

return total

})

console.log(average)//3

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Code 61: Convert 2D/3D array into 1D using reduce function and inbuilt function i.e flat

const arr = [

['a','b'],

['c','d'],

['e','f'],

]

const flatArr = arr.reduce((accum, curr)=>{

return accum.concat(curr)

})

console.log(flatArr) //["a", "b", "c", "d", "e", "f"]

OR

const arr = [

['a','b'],

['c','d'],

['e',['f','g']],

]

console.log(arr.flat(2)) //["a", "b", "c", "d", "e", "f"] //bydefault 1 hota h as a argument

OR

const arr = [

['a','b'],

['c','d'],

['e',['f',['g','h']]],

]

console.log(arr.flat(3)) //["a", "b", "c", "d", "e", "f", "g", "h"]

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code 62: Reverse of a nuber using converting into string

function reverseNumber(input){

return(

parseFloat(input.toString().split('').reverse().join(''))*Math.sign(input)

)

}

console.log(reverseNumber(123)) //321

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code 63: Reverse of a nuber

function reverseNumber(input){

var result=0;

while(input!=0){ //123 //12 //1

result = result *10; //0*10=0 //3*10=30 // 32*10 =320

result = result + (input%10) //give reminder // 0+3=3 // 30+2=32 //320+1=321

input = Math.floor(input/10) //12 //1

// console.log("in", input)

}

return result

}

console.log(reverseNumber(123)) //321

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code 64: Check Armstrong Number

function CheckArmstrongNum(num){ //153

var temp = num;

var result =0;

var a;

while(temp>0){ //153 //15 //1

a= temp%10; //3 //5 //1

temp= parseInt(temp/10) //15 // 1

result= result+a*a*a //0+3*3*3 // 27+ 5*5*5 // 27+ 5*5*5 +1*1*1

}

if(result==num){

return true

}

return false

}

console.log(CheckArmstrongNum(153)) //3*3*3 + 5*5*5 + 1*1*1

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code 65: To find the closest number in an array

const needle = 5;

const numbers = [1, 10, 7, 2, 4, 9];

numbers.sort((a, b) => {

return Math.abs(needle - a) - Math.abs(needle - b);

})

console.log(numbers[0]);

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code 66: To find the second largest number

function secondLargestNum(arr){

return arr.sort((a, b)=> b - a )[1]

}

console.log(secondLargestNum(['1', '2', '3', '4', '9']))

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code 67: To check whether particular word/number present in sentence or not using inbuilt function

function wordInSentence(str){

return str.includes("world"); //true

}

console.log(wordInSentence("Hello world, welcome to the universe."))

OR

var nums =[0,1,3,5,6,7,8,9,7]

console.log(nums.includes(9)) //true

OR

var item=3

console.log(nums.some(x => x === item)) //true

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code 68: To check whether particular word/number present in sentence or not using custom function

function checkValueExist(arr, item){

var status = "Not Exist"

for(var i=0; i<arr.length; i++){

if(arr[i]===item){

status = "Exist"

break;

}

}

return status

}

console.log(checkValueExist(['priya', 'riya', 'supriya'], 'priya'))

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code 69: To check wheather property exist or not in object

let student ={

name : "priya",

age: 20