JavaScript Specific problems

📄️ Counter

Given an integer n, return a counter function. This counter function initially returns n and then returns 1 more than the previous value every subsequent time it is called (n, n + 1, n + 2, etc).

📄️ Sleep

Given a positive integer millis, write an asynchronous function that sleeps for millis milliseconds. It can resolve any value.

📄️ Cache with Time

Write a class that allows getting and setting key-value pairs, however a time until expiration is associated with each key.

📄️ Memoize

Given a function fn, return a memoized version of that function.

📄️ Recursive Flatten

Given a multi-dimensional array arr and a depth n, return a flattened version of that array.

📄️ Array Reduce Transformation

Given an integer array nums, a reducer function fn, and an initial value init, return a reduced array.

📄️ Function Composition

Given an array of functions [f1, f2, f3, ..., fn], return a new function fn that is the function composition of the array of functions.

📄️ Filter Elements From Array

Given an integer array arr and a filtering function fn, return a filtered array filteredArr.

📄️ Group By

Write code that enhances all arrays such that you can call the array.groupBy(fn) method on any array and it will return a grouped version of the array.

📄️ Promise Time Limit

Given an asynchronous function fn and a time t in milliseconds, return a new time limited version of the input function. fn takes arguments provided to the time limited function.

📄️ Fibonnacci

Write a generator function that returns a generator object which yields the fibonacci sequence.

📄️ Nested Array Generator

Given a multi-dimensional array of integers, return a generator object which yields integers in the same order as inorder traversal.

📄️ Counter Two

Write a function createCounter. It should accept an initial integer init. It should return an object with three functions.

Design an EventEmitter class. This interface is similar (but with some differences) to the one found in Node.js or the Event Target interface of the DOM. The EventEmitter should allow for subscribing to events and emitting them.

📄️ To Be or Not To Be

Write a function expect that helps developers test their code. It should take in any value val and return an object with the following two functions.

📄️ Execute Asynchronous Functions In Parallel

Given an array of asynchronous functions functions, return a new promise promise. Each function in the array accepts no arguments and returns a promise.

📄️ Compact Object

Given an object or array obj, return a compact object. A compact object is the same as the original object, except with keys containing falsy values removed. This operation applies to the object and any nested objects. Arrays are considered objects where the indices are keys. A value is considered falsy when Boolean(value) returns false.

📄️ Join Two Arrays By Id

Given two arrays arr1 and arr2, return a new array joinedArray. All the objects in each of the two inputs arrays will contain an id field that has an integer value. joinedArray is an array formed by merging arr1 and arr2 based on their id key. The length of joinedArray should be the length of unique values of id. The returned array should be sorted in ascending order based on the id key.

📄️ Array Prototype Last

Write code that enhances all arrays such that you can call the array.last() method on any array and it will return the last element. If there are no elements in the array, it should return -1.

📄️ Reverse words in a string

Given an input string s, reverse the order of the words.

📄️ Zigzag Conversion

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

📄️ Merge Sorted Array

You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively.

📄️ Valid Palindrome

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

📄️ Two Sum II

Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 < numbers.length.