We have to write a recursive function fibonacci() that takes in a number n and returns an array with first n elements of fibonacci series. Therefore, let’s write the code for this function −Exampleconst fibonacci = (n, res = [], count = 1, last = 0) => {    if(n){       return fibonacci(n-1, res.concat(count), count+last, count);    };    return res; }; console.log(fibonacci(8)); console.log(fibonacci(0)); console.log(fibonacci(1)); console.log(fibonacci(19));OutputThe output in the console will be −[    1, 1, 2, 3,    5, 8, 13, 21 ] [] [ 1 ] [    1, 1, 2, 3, 5,    8, 13, 21, 34, 55,    89, 144, 233, 377, 610,    987, 1597, 2584, 4181 ]

We have an array of string literals like this −const arr = ['Some', 'random', 'words', 'that', 'actually', 'form', 'a', 'sentence.'];We are required to write a function that returns the longest and the shortest word from this array. We will use Array.prototype.reduce() method to keep track of the longest and shortest word in the array through a complete iteration.The code for this will be −Exampleconst arr = ['Some', 'random', 'words', 'that', 'actually', 'form', 'a', 'sentence.']; const findWords = (arr) => {    return arr.reduce((acc, val) => {       const { length: len } = val;       if(len ... Read More

Let’s say, we have to write a function that takes in an array and returns another array in which the consecutive similar numbers are added up together.For example −const array = [1, 5, 5, 5, 8, 8, 9, 1, 4, 4, 2];The output should be −[1, 15, 16, 9, 1, 8, 2]All consecutive 5s added up to 15, then 2 consecutive 8s added up to 16 similarly 4s added up to 8.Therefore, let’s write the code for this function. We will use the Array.prototype.reduce() method here to reduce the original array and simultaneously construct a new one.Exampleconst array = [1, ... Read More

We have to write a function, say searchRecursively() that takes in an array and a search query and returns the count of that search query in the nested array.For example, if the array is given by −const names = ["rakesh", ["kalicharan", "krishna", "rakesh", "james", ["michael", "nathan", "rakesh", "george"]]];Then −searchRecursively(names, ‘’rakesh’);Should return 3 because it makes a total of 3 appearances in the array. Therefore, let’s write the code for this recursive function −Exampleconst names = ["rakesh", ["kalicharan", "krishna", "rakesh", "james", ["michael", "nathan", "rakesh", "george"]]]; const searchRecursively = (arr, query, count = 0, len = 0) => {    if(len < ... Read More

We have to write a function that takes in two objects, merges them into a single object, and adds the values for same keys. This has to be done in linear time and constant space, means using at most only one loop and merging the properties in the pre-existing objects and not creating any new variable.So, let’s write the code for this function −Exampleconst obj1 = {    value1: 45,    value2: 33,    value3: 41,    value4: 4,    value5: 65,    value6: 5,    value7: 15, }; const obj2 = {    value1: 34,    value3: 71,   ... Read More

We are required to write a function that takes in a string of roman number and returns its decimal (base 10) equivalent. Therefore, let’s write the code for this function −Exampleconst romanToInt = (s) => {    const legend = "IVXLCDM";    const l=[1, 5, 10, 50, 100, 500, 1000];    let sum=0;    while(s){       if(!!s[1] && legend.indexOf(s[0]) < legend.indexOf(s[1])){          sum += (l[legend.indexOf(s[1])] - l[legend.indexOf(s[0])]);          s = s.substring(2, s.length);       } else {          sum += l[legend.indexOf(s[0])];          s = s.substring(1, ... Read More

Let’s say, we are required to write a function, say intToRoman(), which, as the name suggests, returns a Roman equivalent of the number passed in it as an argument.Let’s write the code for this function −Exampleconst intToRoman = (num) => {    let result = "";    while(num){       if(num>=1000){          result += "M";          num -= 1000;       }else if(num>=500){          if(num>=900){             result += "CM";             num -= 900;          }else{   ... Read More

We have an array of elements that contains both truth and false values. Our job is to write a function that returns an array with indices of those elements which are NaN in the original array.NaN !== NaNThe datatype of NaN is actually number. Although NaN is a falsy value, it has a peculiar property that no other datatype or variable has. It’s that the expression NaN === NaN yields false. And it’s only in the case of NaN that its false.So, we can use this behavior to our good and pick out NaN value index. The code for this ... Read More

Let’s say, we have two arrays both containing String literals, one of which is required to sort alphabetically, but if this array, the one we have to sort contains some words from the other array, those words should appear at the very top and the rest of the element should be sorted alphabetically.Let’s write a function, say excludeSorting(arr, ex) where arr is the array to be sorted and ex is the array of strings that should appear at top in arr (if they appear in arr).Exampleconst arr = ['apple', 'cat', 'zebra', 'umbrella', 'disco', 'ball', 'lemon', 'kite', 'jack', 'nathan']; const toBeExcluded ... Read More

Let’s say, we have to write a function that takes in a number and returns an array of numbers with elements as the digits of the number but in reverse order. We will convert the number into a string, then split it to get an array of strings of digit, then we will convert the string into numbers, reverse the array and finally return it.Following is our function that takes in a number to be reversed −const reversifyNumber = (num) => {    const numString = String(num);    return numString.split("").map(el => {       return +el;    }).reverse(); };Exampleconst ... Read More