Luyện JS Coding

Write mergeSorted(a, b) merging two sorted arrays into one sorted array, without sort()

Write mostFrequentChar(str) returning the most frequent character (null for an empty string)

Write isAnagram(a, b) checking whether two strings are anagrams (ignoring case and spaces)

Write twoSum(nums, target) returning the indices of the two numbers adding up to target (empty array if none)

Write groupByLength(words) that groups an array of strings into an object keyed by length

Write flatten(arr) that flattens a nested array at any depth

Write chunk(arr, size) that splits an array into groups of size

Write titleCase(str) that uppercases the first letter of every word and lowercases the rest

Write fizzBuzz(n) returning the FizzBuzz sequence from 1 to n as an array of strings

Write countVowels(str) that counts the vowels in a string