Javascript code explainers

javascript

class Stack {
  #items = [];
 
  push(value) {

Building a Stack with private fields

data-structures encapsulation iterators

Intermediate 7 steps

javascript

function depthFirstSearch(graph, start) {
  const visited = new Set();
  const order = [];

Depth-first search and pathfinding in JS

graphs recursion depth-first-search

Intermediate 8 steps

javascript

// Sliding window maximum using a monotonic decreasing deque.
// Returns an array of the maximum value within each window of size k.
function maxSlidingWindow(nums, k) {
  const result = [];

Sliding window maximum with a deque

sliding-window monotonic-deque amortized-analysis

Advanced 7 steps

javascript

function debounce(fn, delay) {
  let timeoutId = null;
 
  function debounced(...args) {

Building a debounce function in JavaScript

closures timers higher-order-functions

Intermediate 6 steps

javascript

function flatten(arr) {
  const result = [];
  for (const item of arr) {
    if (Array.isArray(item)) {

Flattening nested arrays with recursion

recursion arrays reduce

Intermediate 7 steps

javascript

function getCityName(user) {
  return user?.address?.city ?? "Unknown city";
}

Optional chaining and nullish coalescing in JS

optional-chaining nullish-coalescing defensive-coding

Intermediate 5 steps

javascript

function throttle(fn, wait) {
  let lastCall = 0;
  let timeoutId = null;
  let lastArgs = null;

Building a leading-and-trailing throttle

closures rate-limiting timers

Advanced 6 steps

javascript

async function* fetchPages(baseUrl, maxPages) {
  let page = 1;
  while (page <= maxPages) {
    const data = await mockFetch(`${baseUrl}?page=${page}`);

Paginated APIs with async generators

async-iterators generators pagination

Advanced 7 steps

javascript

const PENDING = 'pending';
const FULFILLED = 'fulfilled';
const REJECTED = 'rejected';

Building a Promise from scratch

promises state-machine microtasks

Advanced 10 steps

javascript

function delegate(root, eventType, selector, handler) {
  const listener = (event) => {
    let node = event.target;
    while (node && node !== root) {

Event delegation with a clean teardown

event-delegation dom closures

Intermediate 8 steps