React code explainers

javascript

import { useReducer, useEffect } from "react";
 
const initialState = { status: "idle", data: null, error: null };

Building a data-fetching hook in React

custom-hooks usereducer data-fetching

Intermediate 9 steps

javascript

import { useState, useEffect, useCallback } from 'react';
 
function getColumnCount(width) {
  if (width < 640) return 1;

A responsive column hook in React

custom-hooks debouncing responsive-design

Intermediate 7 steps

javascript

import { useEffect, useState } from 'react';
 
export function useJobStatus(jobId, { interval = 3000 } = {}) {
  const [status, setStatus] = useState('pending');

Polling a job status with a React hook

custom-hooks polling cleanup

Intermediate 8 steps

javascript

function useHashState(key, defaultValue) {
  const parse = () => {
    const params = new URLSearchParams(window.location.hash.slice(1));
    return params.has(key) ? params.get(key) : defaultValue;

A React hook backed by the URL hash

custom-hooks url-state event-listeners

Intermediate 6 steps

javascript

import { useEffect, useRef } from "react";
import { useLocation } from "react-router-dom";
 
export function RouteFocus({ title, children }) {

Managing focus on route change in React

accessibility focus-management routing

Intermediate 6 steps

javascript

import { useState, useRef, useCallback } from "react";
 
export function MultiSelect({ options, value, onChange, placeholder = "Select…" }) {
  const [open, setOpen] = useState(false);

Building a keyboard-accessible MultiSelect in React

controlled-component accessibility keyboard-navigation

Intermediate 10 steps

typescript

import { useCallback, useEffect, useRef, useState } from "react";
 
interface Page<T> {
  items: T[];

A cursor-based infinite scroll hook in React

custom-hooks pagination intersection-observer

Intermediate 9 steps

javascript

import { useState, useEffect, useCallback } from 'react';
 
export function useCountdown(initialSeconds) {
  const [secondsLeft, setSecondsLeft] = useState(initialSeconds);

Building a useCountdown hook in React

custom-hooks state-management side-effects

Intermediate 8 steps

javascript

import { useState, useRef } from "react";
 
export function TagInput({ initialTags = [], onChange }) {
  const [tags, setTags] = useState(initialTags);

Building a tag input in React

controlled-inputs state-management keyboard-handling

Intermediate 8 steps

javascript

import { NavLink, useLocation } from 'react-router-dom';
 
const NAV_ITEMS = [
  { to: '/', label: 'Dashboard', end: true },

Building an accessible Sidebar in React

routing accessibility declarative-ui

Intermediate 6 steps

javascript

import { useEffect, useRef } from "react";
import { useBlocker } from "react-router-dom";
 
export function useUnsavedChangesPrompt(isDirty, message = "You have unsaved changes. Leave anyway?") {

Guarding unsaved changes with a React hook

custom-hooks navigation-guard event-listeners

Intermediate 7 steps

javascript

import { forwardRef, useImperativeHandle, useRef, useState } from 'react';
 
const TextField = forwardRef(function TextField(
  { label, error, onChange, ...props },

Exposing an imperative handle in React

forwardref useimperativehandle refs

Advanced 8 steps

typescript

import { useState, useCallback } from 'react';
 
type Todo = {
  id: string;

Optimistic UI updates in a React hook

optimistic-updates custom-hooks error-handling

Intermediate 8 steps

javascript

import { createContext, useContext, useState, useId } from "react";
 
const AccordionContext = createContext(null);
const ItemContext = createContext(null);

Building a compound Accordion in React

context compound-components state-management

Intermediate 8 steps

javascript

import { useState, useCallback, useRef } from 'react';
 
function LikeButton({ postId, initialLiked, initialCount }) {
  const [liked, setLiked] = useState(initialLiked);

Optimistic like button with React

optimistic-ui abortcontroller error-handling

Advanced 7 steps

javascript

import { useState, useRef, useEffect, useCallback } from 'react';
 
export function CopyButton({ text, label = 'Copy' }) {
  const [copied, setCopied] = useState(false);

A copy-to-clipboard button in React

clipboard-api hooks cleanup

Intermediate 7 steps

javascript

import { createContext, useContext, useEffect, useState, useCallback } from 'react';
 
const ThemeContext = createContext(null);

Building a theme provider with React Context

context hooks dark-mode

Intermediate 9 steps

javascript

import { useState } from 'react';
 
const steps = ['account', 'profile', 'review'];

Building a multi-step form wizard hook in React

custom-hooks form-validation state-management

Intermediate 9 steps