If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Finish the solution so that it returns the sum of all the multiples of 3 or 5 below the number passed in.
Note: If the number is a multiple of both 3 and 5, only count it once. Also, if a number is negative, return 0.
const solution = number => {
// Your solution
};
console.log(solution(0)); // 0
console.log(solution(-15)); // 0
console.log(solution(10)); // 23
console.log(solution(20)); // 78
console.log(solution(200)); // 9168Solution
const solution = number => {
let sum = 0;
for (let i = 3; i < number; i++) {
if (i % 3 === 0 || i % 5 === 0) {
sum += i;
}
}
return sum;
};Create a function that takes an integer as an argument and returns "Even" for even numbers or "Odd" for odd numbers.
const even_or_odd = number => {
// Your solution
};
console.log(even_or_odd(0)); // 'Even'
console.log(even_or_odd(2)); // 'Even'
console.log(even_or_odd(3)); // 'Odd'
console.log(even_or_odd(-3)); // 'Odd'Solution
const even_or_odd = number => {
return number % 2 === 0 ? 'Even' : 'Odd';
};The clock shows h hours (0 <= h <= 23), m minutes (0 <= m <= 59) and s seconds (0 <= s <= 59) after midnight. Your task is to write a function which returns the time since midnight in milliseconds.
const past = (h, m, s) => {
// Your solution
}
console.log(past(0, 0, 0)); // 0
console.log(past(0, 1, 1)); // 61000
console.log(past(1, 0, 0)); // 3600000
console.log(past(1, 0, 1)); // 3601000
console.log(past(1, 1, 1)); // 3661000Solution
const past = (h, m, s) => {
return ((h * 60 * 60) + (m * 60) + s) * 1000;
}Write a function that given the input string name, returns the greeting statement Hello, <name> how are you doing today?
const greet = name => {
//Your solution
}
console.log(greet("Ryan")); // "Hello, Ryan how are you doing today?"
console.log(greet("Sara")); // "Hello, Sara how are you doing today?"Solution
const greet = name => {
return `Hello, ${name} how are you doing today?`;
}The first century spans from the year 1 up to and including the year 100, The second - from the year 101 up to and including the year 200, etc. Given a year, return the century it is in.
const century = year => {
// Your solution
}
console.log(century(1705)); // 18
console.log(century(1900)); // 19
console.log(century(1601)); // 17
console.log(century(2000)); // 20
console.log(century(89)); // 1Solution
const century = year => {
return Math.ceil(year / 100);
}Nathan loves cycling. Because Nathan knows it is important to stay hydrated, he drinks 0.5 litres of water per hour of cycling. You get given the time in hours and you need to return the number of litres Nathan will drink, rounded to the smallest value.
const litres = time => {
// Your solution
}
console.log(litres(0)); // 0
console.log(litres(2)); // 1
console.log(litres(1.4)); // 0
console.log(litres(12.3)); // 6
console.log(litres(0.82)); // 0
console.log(litres(11.8)); // 5
console.log(litres(1787)); // 893Solution
const litres = time => {
return Math.floor(time / 2);
}Create a function that checks if a number n is divisible by two numbers x AND y. All inputs are positive, non-zero digits.
const isDivisible = (n, x, y) => {
// Your solution
}
console.log(isDivisible(3, 3, 4)); // false
console.log(isDivisible(12, 3, 4)); // true
console.log(isDivisible(8, 3, 4)); // false
console.log(isDivisible(48, 3, 4)); // trueSolution
const isDivisible = (n, x, y) => {
return (n % x === 0) && (n % y ===0);
}Return the number (count) of vowels (a, e, i, o, u) in the given string. The input string will only consist of lower case letters and/or spaces.
const getCount = str => {
// Your solution
}
console.log(getCount('my pyx')); // 0
console.log(getCount('pear tree')); // 4
console.log(getCount('abracadabra')); // 5
console.log(getCount('o a kak ushakov lil vo kashu kakao')); // 13Solution
const getCount = str => {
let vowelsCount = 0;
for (let char of str) {
if ('aeiou'.includes(char)) vowelsCount++;
}
return vowelsCount;
};Trolls are attacking your comment section! A common way to deal with this situation is to remove all of the vowels from the trolls' comments, neutralizing the threat. Your task is to write a function that takes a string and returns a new string with all vowels (a, e, i, o, u) removed.
const disemvowel = str => {
// Your solution
}
console.log(disemvowel('This website is for losers LOL!')); // 'Ths wbst s fr lsrs LL!'Solution
const disemvowel = str => {
return str.replace(/[aeiou]/gi, '');
}Given an array of integers, find the one that appears an odd number of times. There will always be only one integer that appears an odd number of times.
const findOdd = arr => {
// Your solution
}
console.log(findOdd([20, 1, -1, 2, -2, 3, 3, 5, 5, 1, 2, 4, 20, 4, -1, -2, 5])); // 5
console.log(findOdd([20, 1, 1, 2, 2, 3, 3, 5, 5, 4, 20, 4, 5])); // 5
console.log(findOdd([1, 1, 2, -2, 5, 2, 4, 4, -1, -2, 5])); // -1
console.log(findOdd([5, 4, 3, 2, 1, 5, 4, 3, 2, 10, 10])); // 1
console.log(findOdd([1, 1, 1, 1, 1, 1, 10, 1, 1, 1, 1])); // 10
console.log(findOdd([10])); // 10Solution
const findOdd = arr => {
return arr.reduce((a, b) => a ^ b);
}Given a word, your job is to return the middle character(s) of the word. If the word's length is odd, return the middle character. If the word's length is even, return the middle 2 characters.
const getMiddle = str => {
// Your solution
}
console.log(getMiddle('test')); // 'es'
console.log(getMiddle('testing')); // 't'
console.log(getMiddle('middle')); // 'dd'
console.log(getMiddle('A')); // 'A'Solution
const getMiddle = str => {
const midIndex = str.length / 2 ;
return str.length % 2 ? str[Math.floor(midIndex)] : str[midIndex - 1] + str[midIndex];
}You probably know the "like" system from Facebook and other social media. People can "like" posts, photos or other items. We want to create the text that should be displayed next to such an item.
Implement a function that takes an input array, containing the names of people who like an item and returns an output string formatted nicely as shown below.
const likes = names => {
// Your solution
}
console.log(likes([])); // 'no one likes this'
console.log(likes(['Peter'])); // 'Peter likes this'
console.log(likes(['Jacob', 'Alex'])); // 'Jacob and Alex like this'
console.log(likes(['Max', 'John', 'Mark'])); // 'Max, John and Mark like this'
console.log(likes(['Alex', 'Jacob', 'Mark', 'Max'])); // 'Alex, Jacob and 2 others like this'Solution
const likes = names => {
let output;
if (names.length === 0) {
output = 'no one likes this';
} else if (names.length === 1) {
output = `${names[0]} likes this`;
} else if (names.length === 2) {
output = `${names[0]} and ${names[1]} like this`;
} else if (names.length === 3) {
output = `${names[0]}, ${names[1]} and ${names[2]} like this`;
} else {
output = `${names[0]}, ${names[1]} and ${names.length - 2} others like this`;
}
return output;
}Write a function that accepts an array of 10 integers (between 0 and 9), and returns a string of those numbers in the form of a phone number.
const createPhoneNumber = numbers => {
// Your solution
}
console.log(createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0])); // '(123) 456-7890'
console.log(createPhoneNumber([1, 1, 1, 1, 1, 1, 1, 1, 1, 1])); // '(111) 111-1111'
console.log(createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0])); // '(123) 456-7890'Solution
const createPhoneNumber = numbers => {
// Using RegEx
return numbers.join('').replace(/(\d{3})(\d{3})(\d+)/, '($1) $2-$3');
// Using reduce()
// return numbers.reduce((acc, cur) => acc.replace('x', cur), '(xxx) xxx-xxxx');
}Given an integer, your task is to square every digit of it and concatenate them to produce a new integer.
const squareDigits = num => {
// Your solution
}
console.log(squareDigits(2112)); // 4114
console.log(squareDigits(3212)); // 9414
console.log(squareDigits(9159)); // 8112581Solution
const squareDigits = num => {
return Number(num.toString().split('').map(ele => ele * ele).join(''));
}Write a function that given an integer, checks to see if it is a square number. A square number or perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself.
const isSquare = n => {
// Your solution
};
console.log(isSquare(0)); // true
console.log(isSquare(4)); // true
console.log(isSquare(25)); // true
console.log(isSquare(3)); // false
console.log(isSquare(93)); // false
console.log(isSquare(-1)); // falseSolution
const isSquare = n => {
return Math.sqrt(n) % 1 === 0;
};Given a string of space-separated numbers, write a function that returns the highest and lowest numbers. There will always be at least one number in the input string.
const highAndLow = numbers => {
// Your solution
}
console.log(highAndLow('1 2 3 4 5')); // '5 1'
console.log(highAndLow('1 2 -3 4 5')); // '5 -3'
console.log(highAndLow('1 9 3 4 -5')); // '9 -5'
console.log(highAndLow('0 -214 542')); // '542 -214'Solution
const highAndLow = numbers => {
const arr = numbers.split(' ');
return `${Math.max(...arr)} ${Math.min(...arr)}`;
}Write a function that takes any non-negative integer as an argument and returns it with its digits in descending order. Essentially, rearrange the digits to create the highest possible number.
const descendingOrder = n => {
// Your solution
}
console.log(descendingOrder(0)); // 0
console.log(descendingOrder(1)); // 1
console.log(descendingOrder(1021)); // 2110
console.log(descendingOrder(42145)); // 54421
console.log(descendingOrder(145263)); // 654321
console.log(descendingOrder(123456789)); // 987654321Solution
const descendingOrder = n => {
return parseInt(n.toString().split('').sort().join(''));
}Given a string which includes only letters, write a function that produces the outputs below.
const accum = str => {
// Your solution
}
console.log(accum('abcd')); // 'A-Bb-Ccc-Dddd'
console.log(accum('cwAt')); // 'C-Ww-Aaa-Tttt'
console.log(accum('RqaEzty')); // 'R-Qq-Aaa-Eeee-Zzzzz-Tttttt-Yyyyyyy'Solution
const accum = str => {
return str.split('').map((ele, index) => ele.toUpperCase() + ele.toLowerCase().repeat(index)).join('-');
}Write a function that takes in a string of one or more words, and returns the same string, but with all five or more letter words reversed. Strings passed in will consist of only letters and spaces.
const spinWords = str => {
// Your solution
}
console.log(spinWords('This is a test')); // 'This is a test'
console.log(spinWords('Hey fellow warriors')); // 'Hey wollef sroirraw'
console.log(spinWords('This is another test')); // 'This is rehtona test'Solution
const spinWords = str => {
return str.split(' ').map(word => word.length < 5 ? word : word.split('').reverse().join('')).join(' ');
}Given a non-empty string of words, return the length of the shortest word(s).
const findShort = str => {
// Your solution
}
console.log(findShort("Test where final word shortest see")); // 3
console.log(findShort("Lets all go on holiday somewhere very cold")); // 2
console.log(findShort("i want to travel the world writing code one day")); // 1Solution
const findShort = str => {
return Math.min(...str.split(' ').map(word => word.length));
}Write a function that takes an integer as input, and returns the number of bits that are equal to 1 in the binary representation of that number. You can guarantee that input is non-negative. For example the binary representation of 1234 is 10011010010, so the function should return 5 in this case.
const countBits = n => {
// Your solution
};
console.log(countBits(0)); // 0
console.log(countBits(4)); // 1
console.log(countBits(7)); // 3
console.log(countBits(9)); // 2Solution
const countBits = n => {
return n.toString(2).split('0').join('').length;
};Check to see if a string has the same amount of 'x's and 'o's. The method must return a boolean and be case insensitive. The input string can contain any character.
const XO = str => {
// Your solution
}
console.log(XO('xo')); // true
console.log(XO('Oo')); // false
console.log(XO('xxOo')); // true
console.log(XO('xxxm')); // false
console.log(XO('ooom')); // false
console.log(XO("ty")); // true (when no 'x' and 'o' is present should return true)Solution
const XO = str => {
let result = 0;
for (let letter of str.toLowerCase()) {
if (letter === 'x') {
result++;
} else if (letter === 'o') {
result--;
}
}
return !result;
}Given an array of numbers, write a function that returns the sum of all of the positives ones. If the array is empty, the sum should be 0.
const positiveSum = arr => {
// Your solution
};
console.log(positiveSum([1, 2, 3, 4, 5])); // 15
console.log(positiveSum([1, -2, 3, 4, 5])); // 13
console.log(positiveSum([-1, 2, 3, 4, -5])); // 9
console.log(positiveSum([-1, -2, -3, -4, -5])); // 0
console.log(positiveSum([])); // 0Solution
const positiveSum = arr => {
return arr.filter(ele => ele > 0).reduce((a, b) => a + b, 0);
};You are given an array of at least length 3 containing integers. The array is either entirely comprised of odd integers or entirely comprised of even integers except for a single integer N. Write a function that takes the array as an argument and returns this "outlier" N.
const findOutlier = arr => {
// Your solution
};
console.log(findOutlier([0, 1, 2])); // 1
console.log(findOutlier([1, 2, 3])); // 2
console.log(findOutlier([1, 1, 0, 1, 1])); // 0
console.log(findOutlier([0, 0, 3, 0, 0])); // 3
console.log(findOutlier([160, 3, 1719, 19, 13, -21])); // 160
console.log(findOutlier([4, 0, 100, 4, 11, 2602, 36])); // 11Solution
const findOutlier = arr => {
const even = arr.filter(ele => ele % 2 === 0);
const odd = arr.filter(ele => ele % 2 !== 0);
return even.length === 1 ? even[0] : odd[0];
};Write a function that subtracts one list from another and returns the result. It should remove all values from array a, which are present in array b.
const arrayDiff = (a, b) => {
// Your solution
};
console.log(arrayDiff([1,8,2], [])); // [1, 8, 2]
console.log(arrayDiff([1,2,3], [1,2])); // [3]
console.log(arrayDiff([3,4], [3])); // [4]
console.log(arrayDiff([], [4,5])); // []Solution
const arrayDiff = (a, b) => {
return a.filter(ele => !b.includes(ele));
};Write a function that capitalizes each word in a given input string.
String.prototype.capitalize = function () {
// Your solution
};
var str = "How can mirrors be real if our eyes aren't real";
console.log(str.capitalize()); // 'How Can Mirrors Be Real If Our Eyes Aren't Real'Solution
String.prototype.capitalize = function () {
return this.split(' ').map(ele => ele[0].toUpperCase() + ele.slice(1)).join(' ');
};DNA is a chemical found in the nucleus of cells and carries the "instructions" for the development and functioning of living organisms. In DNA strings, symbols "A" and "T" are complements of each other, as are "C" and "G". Given one side of the DNA, write a function that returns the other complementary side. The DNA strand is never empty.
const DNAStrand = dna => {
// Your solution
}
console.log(DNAStrand('AAAA')); // 'TTTT'
console.log(DNAStrand('ATTGC')); // 'TAACG'
console.log(DNAStrand('GTAT')); // 'CATA'Solution
const DNAStrand = dna => {
const MAP = {
'A': 'T',
'T': 'A',
'G': 'C',
'C': 'G',
}
return [...dna].map(ele => MAP[ele]).join('');
}An isogram is a word that has no repeating letters, consecutive or non-consecutive. Implement a function that determines whether a string that contains only letters is an isogram. Assume the empty string is an isogram. Ignore letter case.
const isIsogram = str => {
// Your solution
}
console.log(isIsogram('Dermatoglyphics')); // true
console.log(isIsogram('isIsogram')); // false
console.log(isIsogram('isogram')); // true
console.log(isIsogram('moOse')); // false
console.log(isIsogram('aba')); // false
console.log(isIsogram('')); // trueSolution
const isIsogram = str => {
return str.length === new Set(str.toLowerCase()).size;
}Write a program that prints the numbers from 1 to 100. But for multiples of
3 prints "Fizz" instead of the number and for the multiples of 5 prints
"Buzz". For numbers which are multiples of both 3 and 5 prints "FizzBuzz".
const fizzBuzz = () => {
// Your solution
}
fizzBuzz(); // 1, 2, 'Fizz', 4, 'Buzz', 'Fizz', 7, ...Solution
const fizzBuzz = () => {
let result;
for (let i = 1; i <= 100; i++) {
result = '';
if (i % 3 === 0) result += 'Fizz';
if (i % 5 === 0) result += 'Buzz';
console.log(result || i);
}
}Write a function that will return the count of distinct case-insensitive alphanumeric characters that occur more than once in the input string.
const duplicateCount = text => {
// Your solution
}
console.log(duplicateCount("")); // 0
console.log(duplicateCount("abcde")); // 0
console.log(duplicateCount("aabbcde")); // 2
console.log(duplicateCount("aabBcde")); // 2, "should ignore case"
console.log(duplicateCount("Indivisibility")); // 1
console.log(duplicateCount("Indivisibilities")); // 2, "characters may not be adjacent"Solution
const duplicateCount = text => {
text = text.toLowerCase();
const freq = {};
for (let letter of text) {
freq[letter] = (freq[letter] || 0) + 1;
}
let result = 0;
for (let letter in freq) {
if (freq[letter] > 1) result++;
}
return result;
}Write a function that converts a string to a new string where each character in the new string is ( if that character appears only once in the original string, or ) if that character appears more than once in the original string. Ignore capitalization when determining if a character is a duplicate.
const duplicateEncode = word => {
// Your solution
}
console.log(duplicateEncode('din')); // '((('
console.log(duplicateEncode('(( @')); // '))(('
console.log(duplicateEncode('recede')); // '()()()'
console.log(duplicateEncode('Success')); // ')())())'Solution
const duplicateEncode = word => {
word = word.toLowerCase();
let result = '';
for (let char of word) {
word.indexOf(char) !== word.lastIndexOf(char)
? result += ')'
: result += '(';
}
return result;
}Write a function that reverses the string that is passed to it. For this challenge, you may NOT use the JavaScript built-in reverse() method.
const reverseString = str => {
// Your solution
}
console.log(reverseString('hello')); // 'olleh'
console.log(reverseString('world')); // 'dlrow'
console.log(reverseString('')); // ''
console.log(reverseString('h')); // 'h'Solution
const reverseString = str => {
let result = '';
for (let char of str) {
result = char + result;
}
return result;
}Write a function that takes a positive number num and returns its multiplicative persistence, which is the number of steps it takes to multiply all the digits of num by each other, and repeating with the product until a single digit is obtained.
const persistence = num => {
// Your solution
}
console.log(persistence(999)); // 4
// because 9*9*9=729, 7*2*9=126, 1*2*6=12, and finally 1*2=2
console.log(persistence(93)); // 3
// because 9*3=27, 2*7=14, 1*4=4 and 4 has only one digit
console.log(persistence(5)); // 0
// because 5 is already a single-digit numberSolution
const persistence = num => {
if (num < 10) return 0;
let product = 1;
while (num >= 10) {
product *= num % 10;
num = Math.floor(num / 10);
}
// Using recursion
return 1 + persistence(product * num);
}Fibonacci number (Fibonacci sequence), named after mathematician Fibonacci, is a sequence of numbers that looks like this: 0, 1, 1, 2, 3, 5, 8, 13,.... You get first two starting numbers, 0 and 1, and the next number in the sequence is always the sum of the previous two numbers.
Write a function fib() that takes one parameter steps, and returns a number from the Fibonacci sequence, based on the parameter steps, which determines the position in Fibonacci number. For example fib(0) returns 0, fib(4) returns 3, and fib(15) returns 610.
const fib = steps => {
// Your solution
};
console.log(fib(0)); // 0
console.log(fib(4)); // 3
console.log(fib(17)); // 1597
console.log(fib(20)); // 6765Solution
// Recursive solution
const fib = steps => {
if (steps < 2) return steps;
return fib(steps - 2) + fib(steps - 1);
};
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