224 articles
RSSHow to fix Deno PermissionDenied (NotCapable in Deno 2) errors — the right permission flags, path-scoped permissions, deno.json permission sets, and the Deno.permissions API.
How to fix Fastify issues — route 404 from plugin encapsulation, reply already sent, FST_ERR_VALIDATION, request.body undefined, @fastify/cors, hooks not running, and TypeScript type inference.
How to fix Apache Kafka issues — consumer not receiving messages, auto.offset.reset, Docker advertised.listeners, max.poll.interval.ms rebalancing, MessageSizeTooLargeException, and KafkaJS errors.
How to fix OpenAI API errors — RateLimitError (429), AuthenticationError (401), APIConnectionError, context length exceeded, model not found, and SDK v0-to-v1 migration mistakes.
How to fix Vinxi server framework issues — app configuration, routers, server functions, middleware, static assets, and deployment to different platforms.
How to fix @formkit/auto-animate issues — parent ref setup, React useAutoAnimate hook, Vue directive, animation customization, disabling for specific elements, and framework integration.
How to fix Blurhash image placeholder issues — encoding with Sharp, decoding in React, canvas rendering, Next.js image placeholders, CSS blur fallback, and performance optimization.
How to fix @clack/prompts issues — interactive CLI prompts, spinners, multi-select, confirm dialogs, grouped tasks, cancellation handling, and building CLI tools with beautiful output.
How to fix CodeMirror 6 issues — basic setup, language and theme extensions, React integration, vim mode, collaborative editing, custom keybindings, and read-only mode.
How to fix Docusaurus issues — docs and blog configuration, sidebar generation, custom theme components, plugin setup, MDX compatibility, search integration, and deployment.
How to fix Embla Carousel issues — React setup, slide sizing, autoplay and navigation plugins, loop mode, thumbnail carousels, responsive breakpoints, and vertical scrolling.
How to fix GSAP animation issues — timeline and tween basics, ScrollTrigger setup, React useGSAP hook, cleanup and context, SplitText, stagger animations, and Next.js integration.
How to fix i18next issues — react-i18next setup, translation file loading, namespace configuration, language detection, interpolation, pluralization, and Next.js integration.
How to fix ky HTTP client issues — instance creation, hooks (beforeRequest, afterResponse), retry configuration, timeout handling, JSON parsing, error handling, and migration from fetch or axios.
How to fix Lottie animation issues — lottie-react and lottie-web setup, JSON animation loading, playback control, interactivity, lazy loading, and performance optimization.
How to fix Mapbox GL JS issues — access token setup, React integration with react-map-gl, markers and popups, custom layers, geocoding, directions, and Next.js configuration.
How to fix pdf-lib issues — creating PDFs from scratch, modifying existing PDFs, embedding fonts and images, form filling, merging documents, and browser and Node.js usage.
How to fix Paraglide.js i18n issues — message compilation, type-safe translations, SvelteKit and Next.js integration, language switching, and message extraction from existing code.
How to fix PostHog analytics issues — JavaScript and Next.js setup, event capture, feature flags, A/B testing, session replay, user identification, and server-side tracking.
How to fix prism-react-renderer issues — Highlight component setup, language support, custom themes, line highlighting, copy button, and integration with MDX and documentation sites.
How to fix Pusher real-time issues — client and server setup, channel types, presence channels, authentication endpoints, event binding, connection management, and React integration.
How to fix react-pdf and @react-pdf/renderer issues — PDF viewer setup, worker configuration, page rendering, text selection, annotations, and generating PDFs in React.
How to fix React Three Fiber (R3F) issues — Canvas setup, loading 3D models with useGLTF, lighting, camera controls, animations with useFrame, post-processing, and Next.js integration.
How to fix Sentry issues — SDK initialization, source map uploads, error boundaries, performance monitoring, Next.js integration, release tracking, and alert configuration.
How to fix Sharp image processing issues — native binary installation, resize and convert operations, Next.js image optimization, Docker setup, serverless deployment, and common platform errors.
How to fix Shiki syntax highlighter issues — basic setup, theme configuration, custom languages, transformer plugins, Next.js and Astro integration, and bundle size optimization.
How to fix View Transitions API issues — same-document transitions, cross-document MPA transitions, view-transition-name CSS, Next.js and Astro integration, custom animations, and browser support.
How to fix Auth.js and NextAuth.js issues — OAuth provider setup, session handling in App Router and Pages Router, JWT vs database sessions, middleware protection, and credential provider configuration.
How to fix Capacitor issues — project setup with Ionic or standalone, native plugin access, iOS and Android build errors, live reload, deep links, push notifications, and migration from Cordova.
How to fix Cypress issues — element selection strategies, async command chaining, cy.intercept for network stubbing, component testing, authentication handling, and flaky test debugging.
How to fix Effect issues — running effects with Effect.runPromise, Layer and service dependency injection, error channel types, Fiber concurrency, Schema validation, and common TypeScript errors.
How to fix Electron issues — main and renderer process setup, IPC communication with contextBridge, preload scripts, auto-update, native module rebuilding, and packaging with electron-builder.
How to fix jose JWT issues — signing and verifying tokens with HS256 and RS256, JWK and JWKS key handling, token expiration, claims validation, and edge runtime compatibility.
How to fix Million.js issues — compiler setup with Vite and Next.js, block() optimization rules, component compatibility constraints, automatic mode, and debugging performance gains.
How to fix Nitro server engine issues — route handlers, middleware, storage with unstorage, caching, WebSocket support, deployment presets for Cloudflare Workers, Vercel, and Node.js.
How to fix Panda CSS issues — PostCSS setup, panda.config.ts token system, recipe and pattern definitions, conditional styles, responsive design, and integration with Next.js and Vite.
How to fix Qwik issues — component$ boundaries, useSignal and useStore reactivity, serialization with dollar signs, useTask$ and useVisibleTask$, Qwik City routing, and integration with React components.
How to fix Radix UI issues — Popover and Dialog setup, controlled vs uncontrolled state, portal rendering, animation with CSS or Framer Motion, accessibility traps, and Tailwind CSS integration.
How to fix Rspack issues — configuration migration from webpack, loader compatibility, CSS extraction, module federation, React Fast Refresh, and build performance tuning.
How to fix Svelte 5 Runes issues — $state and $state.raw reactivity, $derived computations, $effect lifecycle, $props and $bindable, migration from Svelte 4 stores, and component patterns.
How to fix UnoCSS issues — Vite plugin setup, preset configuration, attributify mode, icons preset, shortcuts, custom rules, and integration with Next.js, Nuxt, and Astro.
How to fix Wrangler and Cloudflare Workers issues — wrangler.toml configuration, KV and D1 bindings, R2 storage, environment variables, local dev with Miniflare, and deployment troubleshooting.
How to fix Biome linter/formatter issues — biome.json configuration, migrating from ESLint and Prettier, VSCode extension setup, CI integration, and rule override syntax.
How to fix Convex backend issues — query/mutation/action patterns, schema validation, real-time reactivity, file storage, auth integration, and common TypeScript type errors.
How to fix date-fns issues — timezone handling with date-fns-tz, parseISO vs new Date, locale import and configuration, DST edge cases, v3 ESM migration, and common format pattern mistakes.
How to fix dnd-kit issues — DndContext setup, sensors configuration, useSortable with SortableContext, drag overlays, collision detection algorithms, and accessible drag and drop.
How to fix esbuild issues — entry points, plugin API, JSX configuration, CSS modules, watch mode, metafile analysis, external packages, and common migration problems from webpack.
How to fix Expo issues — Expo Go vs development builds, native module installation with expo-modules-core, EAS Build configuration, bare workflow setup, and common SDK upgrade problems.
How to fix Framer Motion issues — variants, AnimatePresence for exit animations, layout animations, useMotionValue, server component errors, and performance optimization.
How to fix Git hooks not executing — Husky v9 setup, hook file permissions, lint-staged configuration, pre-commit Python tool, lefthook, and bypassing hooks in CI.
How to fix Hono framework issues — routing order, middleware chaining, Hono RPC type inference, Cloudflare Workers bindings, validator integration, and runtime compatibility.
How to fix HTMX issues — attribute syntax, target and swap strategies, out-of-band swaps, event handling, CSP configuration, response headers, and debugging HTMX requests.
How to fix Jotai state management issues — atom scope, derived atoms, async atoms with Suspense, atomWithStorage SSR, useAtomValue vs useSetAtom, and debugging stale state.
How to fix Lucia auth issues — adapter setup, session validation in middleware, cookie configuration, OAuth provider integration, Next.js App Router setup, and Lucia v3 migration.
How to fix MDX issues — Next.js App Router setup with @next/mdx and next-mdx-remote, custom component mapping, frontmatter parsing with gray-matter, remark and rehype plugins, and TypeScript configuration.
How to fix Mock Service Worker issues — browser vs Node setup, handler registration, worker start timing, passthrough requests, and common MSW v2 API changes from v1.
How to fix next-intl issues — App Router setup with middleware, useTranslations in server and client components, locale detection, pluralization, number and date formatting, and routing configuration.
How to fix Nuxt 3 issues — useFetch vs $fetch, server routes in server/api, composable SSR rules, useAsyncData, hydration errors, and Nitro configuration problems.
How to fix Playwright test issues — locator strategies, auto-waiting, network mocking, flaky tests in CI, trace viewer debugging, and common headless browser setup problems.
How to fix React Native Reanimated issues — worklet rules, shared values, useAnimatedStyle, Gesture Handler setup, web support, Babel plugin configuration, and Reanimated 3 migration.
How to fix Recharts issues — ResponsiveContainer setup, data format for each chart type, custom tooltips, axis configuration, legends, animations, and TypeScript types.
How to fix Remix issues — loader and action setup, nested route outlet, useLoaderData typing, error boundaries, defer with Await, and common React Router v7 migration problems.
How to fix RxJS issues — subscription management, switchMap vs mergeMap vs concatMap, error handling with catchError, Subject types, cold vs hot observables, and Angular async pipe.
How to fix shadcn/ui issues — Tailwind CSS v4 vs v3 configuration, CSS variables, dark mode setup, component installation, cn() utility, and common errors after adding components.
How to fix SolidJS reactivity issues — signal access inside JSX, effect dependencies, createResource with loading states, Show and For components, store mutations, and common mistakes coming from React.
How to fix Storybook issues — CSF3 story format, addon configuration, webpack vs Vite builder, decorator setup, args not updating component, and Storybook 8 migration problems.
How to fix styled-components issues — ThemeProvider setup, Next.js SSR with ServerStyleSheet, shouldForwardProp, attrs, TypeScript theme typing, and styled-components v6 migration.
How to fix Supabase issues — Row Level Security policies, realtime subscriptions, storage permissions, auth session with Next.js, edge functions, and common client configuration mistakes.
How to fix SvelteKit issues — load function data flow, +page.server.ts vs +page.ts, form actions with use:enhance, hooks.server.ts, SSR vs CSR mode, and common routing mistakes.
How to fix TanStack Query (React Query v5) issues — query keys, stale time, enabled flag, mutation callbacks, optimistic updates, QueryClient setup, and SSR with prefetchQuery.
How to fix TanStack Table (React Table v8) issues — column definitions, server-side sorting and filtering, row selection, virtual rows with TanStack Virtual, and v7 to v8 migration errors.
How to fix Tauri app issues — Rust command registration, invoke IPC, tauri.conf.json permissions, fs scope, window management, and common build errors on Windows/macOS/Linux.
How to fix Tiptap editor issues — useEditor setup in React, StarterKit configuration, custom nodes and marks, SSR with Next.js, collaborative editing, and content serialization.
How to fix Turborepo issues — turbo.json pipeline configuration, cache keys, remote caching setup, workspace filtering, and common monorepo task ordering mistakes.
How to fix Valtio state management issues — proxy vs snapshot, useSnapshot for React, subscribe for side effects, derived state with computed, async actions, and Valtio with React Server Components.
How to fix WebAssembly issues — instantiateStreaming vs instantiate, CORS for WASM files, linear memory limits, wasm-bindgen JS interop, imports/exports mismatch, and WASM in bundlers.
How to fix XState v5 issues — state machine definition, guards and actions typed correctly, useMachine hook, createActor, context updates, child actors, and common v4 to v5 migration errors.
How to fix Zustand state management issues — selector optimization, persist middleware, shallow comparison, devtools setup, slice pattern for large stores, and common subscription mistakes.
How to fix Bun runtime issues — Node.js API compatibility, native addons (node-gyp), Bun.serve vs Node http, bun test differences from Jest, and common package incompatibilities.
How to fix ESLint configuration issues — flat config vs legacy config, extends conflicts, parser options, plugin resolution, per-directory overrides, and migrating to ESLint 9.
How to fix Express middleware issues — middleware execution order, error-handling middleware signature, async error propagation with next(err), and common middleware misconfigurations.
How to fix IndexedDB issues — transaction lifecycle, version upgrades, blocked events, cursor iteration, IDBKeyRange queries, and using idb wrapper library to avoid callback hell.
How to fix Jest setup file issues — setupFilesAfterFramework vs setupFiles, global mocks not applying, @testing-library/jest-dom matchers, module mocking in setup, and TypeScript setup files.
How to fix Pinia store issues — state reactivity with storeToRefs, getters not updating, actions async patterns, store outside components, SSR hydration, and testing Pinia stores.
How to fix React useTransition and startTransition issues — what counts as a transition, Suspense integration, concurrent rendering requirements, and common mistakes that prevent transitions from deferring.
How to fix TypeScript conditional type issues — infer keyword usage, distributive conditional types, deferred evaluation, naked type parameters, and common conditional type patterns.
How to fix TypeScript discriminated union errors — type guards, exhaustive checks, narrowing with in operator, never type, and common patterns for tagged unions.
How to fix TypeScript template literal type errors — string combination types, conditional inference, Extract and mapped types with template literals, and common pitfalls.
How to fix Vue Router params not updating when navigating between same-route paths — watch $route, beforeRouteUpdate, onBeforeRouteUpdate, and component reuse behavior explained.
How to fix Vue 3 slot issues — v-slot syntax, named slots, scoped slots passing data, default slot content, fallback content, and dynamic slot names.
How to fix Web Worker issues — postMessage data cloning, module workers, error handling, SharedArrayBuffer setup, Comlink, and common reasons workers silently fail.
How to fix Zod schema validation issues — parse vs safeParse, transform and preprocess, refine for cross-field validation, discriminatedUnion, error formatting, and common schema mistakes.
How to fix Node.js stream issues — pipe and pipeline errors, backpressure handling, Transform streams, async iteration, error propagation, and common stream anti-patterns.
How to fix React Testing Library query failures — getByRole vs getByText, async queries, accessible names, waitFor patterns, custom queries, and common selector mistakes.
How to fix Vite dev server proxy issues — proxy configuration in vite.config.ts, path rewriting, WebSocket proxying, HTTPS targets, and common misconfigurations.
How to fix Vue Teleport not working — target element not found, SSR with Teleport, disabled prop, multiple Teleports to the same target, and timing issues.
How to fix Jest async test timeouts — missing await, unresolved Promises, done callback misuse, global timeout configuration, fake timers, and async setup/teardown issues.
How to fix Jest coverage not collecting all files — collectCoverageFrom config, coverage thresholds, Istanbul ignore comments, ts-jest setup, and Babel transform issues.
How to fix React's missing key prop warning — why keys matter for reconciliation, choosing stable keys, avoiding index as key pitfalls, keys in fragments, and performance impact.
How to fix React Portal event bubbling — understanding Portal event propagation, modal close on outside click, stopPropagation side effects, focus management, and accessibility.
How to fix React StrictMode double render issues — understanding intentional double invocation, fixing side effects, useEffect cleanup, external subscriptions, and production behavior.
How to fix React Suspense boundaries not triggering — lazy() import syntax, use() hook, data fetching libraries, ErrorBoundary vs Suspense, and Next.js loading.tsx.
How to fix Svelte store subscription memory leaks — auto-subscription with $, manual unsubscribe, derived store cleanup, custom store lifecycle, and SvelteKit SSR store handling.
How to fix TypeScript function overload errors — overload signature compatibility, implementation signature, conditional types as alternatives, method overloads in classes, and common pitfalls.
How to fix TypeScript mapped type errors — Partial, Required, Readonly, Record, Pick, Omit, conditional types, template literal types, and distributive behavior.
How to fix Vue composable reactivity loss — toRefs for destructuring, returning refs vs raw values, reactive object pitfalls, stale closures, and composable design patterns.
How to fix Vue Composition API reactivity loss — destructuring reactive objects, toRefs, storeToRefs, ref vs reactive, watch vs watchEffect, and template not updating.
How to fix Pinia store state not updating components — storeToRefs for destructuring, $patch for partial updates, avoiding reactive() wrapping, getters vs computed, and SSR hydration.
How to reduce Webpack bundle size — code splitting, tree shaking, dynamic imports, bundle analysis, moment.js replacement, lodash optimization, and production build configuration.
How to fix Webpack dev server not reloading — Hot Module Replacement configuration, watchFiles settings, polling for Docker/WSL, HMR API for custom modules, and port conflicts.
How to fix Angular lazy loading not working — loadChildren syntax, standalone components, route configuration mistakes, preloading strategies, and debugging bundle splits.
How to fix RxJS memory leaks in Angular — unsubscribing from Observables, takeUntilDestroyed, async pipe, subscription management patterns, and detecting leaks with Chrome DevTools.
How to fix Angular form validation not working — Reactive Forms vs Template-Driven, custom validators, async validators, touched/dirty state, and error message display.
How to fix Jest fake timers not working — useFakeTimers setup, runAllTimers vs advanceTimersByTime, async timers, React testing with act(), and common timer test mistakes.
How to fix Jest module mocks not working — hoisting behavior, ES module mocks, factory functions, mockReturnValue vs implementation, and clearing mocks between tests.
How to handle Node.js uncaughtException and unhandledRejection events — graceful shutdown, error logging, async error boundaries, and keeping servers alive safely.
How to fix React hydration errors — server/client HTML mismatches, useEffect for client-only code, suppressHydrationWarning, dynamic content, and Next.js specific hydration issues.
How to fix TanStack Query returning stale cached data — staleTime, invalidateQueries, query key structure, optimistic updates, and cache synchronization after mutations.
How to fix Socket.IO CORS errors — server-side CORS configuration, credential handling, polling vs WebSocket transport, proxy setup, and common connection failures.
How to fix TypeScript 'could not find a declaration file for module' errors — installing @types packages, writing custom .d.ts files, module augmentation, and tsconfig paths.
How to fix Vue computed properties not updating — reactive dependency tracking, accessing nested objects, computed setters, watchEffect vs computed, and Vue 3 reactivity pitfalls.
How to fix Vue v-model on custom components — defineModel, modelValue/update:modelValue pattern, multiple v-model bindings, v-model modifiers, and Vue 2 vs Vue 3 differences.
How to fix path alias errors in webpack and Vite — configuring resolve.alias, tsconfig paths, babel-plugin-module-resolver, Vite alias configuration, and Jest moduleNameMapper.
How to fix Angular change detection issues — OnPush strategy not triggering, async pipe, markForCheck vs detectChanges, zone.js and zoneless patterns, and manual change detection triggers.
How to fix CSS container queries not working — setting container-type correctly, understanding containment scope, fixing @container syntax, and handling browser support and specificity issues.
How to fix Express async route handlers not passing errors to the error middleware — wrapping async routes, using express-async-errors, global error handlers, and Node.js unhandledRejection events.
How to fix Jest failing with 'Cannot use import statement outside a module' — configuring Babel transforms, using experimental VM modules, migrating to Vitest, and handling ESM-only packages.
How to fix Next.js App Router fetch caching issues — understanding cache behavior, revalidation with next.revalidate, opting out with no-store, cache tags, and debugging stale data.
How to fix Node.js 'JavaScript heap out of memory' — increasing heap size, finding memory leaks with heap snapshots, fixing common leak patterns, and stream-based processing for large data.
How to fix React Native Android build failures — SDK version mismatches, Gradle errors, duplicate module issues, Metro bundler problems, and NDK configuration for common build errors.
How to fix Redux state not updating in components — mutating state directly, stale selectors, missing immer patterns in Redux Toolkit, useSelector mistakes, and debugging with Redux DevTools.
How to fix Svelte store not updating the UI — writable vs readable stores, derived stores, subscribe pattern, store mutation vs assignment, and custom store patterns.
How to fix Vue Router navigation guards not working — beforeEach, beforeEnter, in-component guards, async guards, redirect loops, and route meta authentication patterns.
How to reduce Webpack bundle size — code splitting, lazy loading, tree shaking, analyzing the bundle with webpack-bundle-analyzer, replacing heavy dependencies, and configuring splitChunks.
How to fix Axios 'Network Error' with no status code — CORS blocks, SSL certificate issues, request timeout, no internet connection, and debugging with interceptors.
How to fix ESLint no-unused-vars false positives — TypeScript types, destructuring ignores, React imports, function arguments, and configuring the rule to match your codebase patterns.
How to fix req.body being undefined in Express — missing body-parser middleware, wrong Content-Type header, middleware order issues, and multipart form data handling.
How to fix CORS errors in Flask — installing flask-cors correctly, handling preflight OPTIONS requests, configuring origins with credentials, route-specific CORS, and debugging missing headers.
How to fix Jest snapshot failures — updating outdated snapshots, removing obsolete ones, fixing inline snapshots, preventing brittle snapshot tests, and managing snapshots in CI.
How to fix CORS errors in Next.js API routes — adding Access-Control headers, handling preflight OPTIONS requests, configuring next.config.js headers, and avoiding common proxy mistakes.
Why React useEffect runs twice in development with Strict Mode, how to handle the double invocation correctly, when to add cleanup functions, and when the double-run actually reveals a real bug.
How to fix TypeScript decorators not applying — experimentalDecorators not enabled, emitDecoratorMetadata missing, reflect-metadata not imported, and decorator ordering issues.
How to fix TypeScript enum problems — const enum with isolatedModules, enums not available at runtime, string vs numeric enums, and migrating to union types or as const objects.
How to fix Vite environment variables showing as undefined — missing VITE_ prefix, wrong .env file for the mode, import.meta.env vs process.env, TypeScript types, and SSR differences.
How to fix CSS custom properties not applying — wrong scope, missing fallback values, JavaScript not setting variables on the right element, and how CSS variables interact with media queries and Shadow DOM.
How to fix Node.js UnhandledPromiseRejectionWarning and process crashes — why unhandled promise rejections crash Node.js 15+, how to add global handlers, find the source of the rejection, and fix async error handling.
How to fix GraphQL 400 Bad Request errors — malformed query syntax, variable type mismatches, missing required fields, schema validation failures, and how to debug GraphQL errors from Apollo and fetch.
How to fix Next.js middleware not executing — wrong file location, matcher config errors, middleware not intercepting API routes, and how to debug middleware execution in Next.js 13 and 14.
How to fix React Query refetching infinitely — why useQuery keeps fetching, how object and array dependencies cause loops, how to stabilize queryKey, and configure refetch behavior correctly.
How to fix Socket.IO connection failures — CORS errors, transport fallback issues, wrong namespace, server not emitting to the right room, and how to debug Socket.IO connections in production.
How to fix TypeScript isolatedModules errors — why const enum fails with Babel and Vite, how to replace const enum, fix re-exported types, and configure isolatedModules correctly for your build tool.
How to fix Vitest configuration not taking effect — why setupFiles don't run, globals are undefined, mocks don't work, and how to configure Vitest correctly for React, Vue, and Node.js projects.
How to fix ESLint's import/no-unresolved errors when modules actually resolve correctly — configure eslint-import-resolver-typescript, fix path alias settings, and handle node_modules that ESLint cannot find.
How to fix jest.mock() not intercepting module calls — why mocks are ignored, how to correctly mock ES modules, default exports, named exports, and fix hoisting issues in Jest tests.
How to fix Next.js build failures — TypeScript errors blocking production builds, module resolution failures, missing environment variables, static generation errors, and common next build crash causes.
How to fix Vite's chunk size warning — why bundles exceed 500 kB, how to split code with dynamic imports and manualChunks, configure the chunk size limit, and optimize your Vite production build.
How to fix JavaScript NaN comparison bugs — why NaN !== NaN, the difference between isNaN() and Number.isNaN(), and how to correctly check for NaN in conditionals and array operations.
How to fix React Native Metro bundler errors — unable to resolve module, EMFILE too many open files, port already in use, transform cache errors, and Metro failing to start on iOS or Android.
How to fix Stripe webhook signature verification errors — why Stripe-Signature header validation fails, how to correctly pass the raw request body, and how to debug webhook delivery in the Stripe dashboard.
How to fix Vue 3 reactive data not updating the UI — why ref and reactive lose reactivity, how to correctly mutate reactive state, and common pitfalls with destructuring and nested objects.
How to fix the JavaScript closure loop bug where all event handlers or setTimeout callbacks return the same value — using let, IIFE, bind, or forEach instead of var in loops.
How to fix React.memo not working — components still re-rendering despite being wrapped in memo, caused by new object/function references, missing useCallback, and incorrect comparison functions.
How to fix TypeScript generic constraint errors — Type 'X' does not satisfy the constraint 'Y', generic inference failures, constrained generics with extends, and conditional types.
How to fix CORS errors in Express.js — cors middleware not applying, preflight OPTIONS requests failing, credentials not allowed, and specific origin whitelisting issues.
How to fix Next.js environment variables returning undefined — NEXT_PUBLIC prefix rules, server vs client context, .env file loading order, and runtime vs build-time variable access.
How to fix React.lazy and Suspense errors — Element type is invalid, A React component suspended while rendering, Loading chunk failed, and lazy import mistakes with named vs default exports.
How to fix Webpack Hot Module Replacement not updating the browser — HMR connection lost, full page reloads instead of hot updates, and HMR breaking in Docker or behind a proxy.
How to fix UnhandledPromiseRejectionWarning in Node.js and unhandled promise rejection errors in JavaScript caused by missing catch handlers, async/await mistakes, and event emitter errors.
How to fix Jest 'Exceeded timeout of 5000ms for a test' errors caused by unresolved promises, missing done callbacks, async/await mistakes, and slow database or network calls in tests.
How to fix React Context not triggering re-renders — caused by mutating state directly, wrong provider placement, stale closures, and missing value changes that React can detect.
How to fix 'No routes matched location' in React Router v6 — caused by missing Routes wrapper, wrong path syntax, nested route mismatches, and v5 to v6 migration issues.
Fix the Electron 'require is not defined' error caused by contextIsolation, nodeIntegration changes, and learn to use preload scripts and contextBridge.
How to fix the Firebase 'permission denied' or 'Missing or insufficient permissions' error in Firestore and Realtime Database. Covers security rules, authentication state, custom claims, Admin SDK, rule simulators, time-based rules, and document-level permissions.
How to fix the Jest 'Cannot find module' error by configuring moduleNameMapper, moduleDirectories, tsconfig paths, and resolving ESM, monorepo, and dependency issues.
How to fix the React 'Warning: Failed prop type' error. Covers wrong prop types, missing required props, children type issues, shape and oneOf PropTypes, migrating to TypeScript, default props, and third-party component mismatches.
How to fix 'SyntaxError: Cannot use import statement outside a module' in Node.js, TypeScript, Jest, and browsers by configuring ESM, package.json type, and transpiler settings.
How to fix Express.js Cannot GET route 404 error caused by wrong route paths, missing middleware, route order issues, static files, and router mounting problems.
How to fix the JavaScript heap out of memory error by increasing Node.js memory limits, fixing memory leaks, and optimizing builds in webpack, Vite, and Docker.
How to fix JavaScript TypeError is not a function caused by wrong variable types, missing imports, overwritten variables, incorrect method names, and callback issues.
How to fix Next.js API route 404 not found errors caused by wrong file paths, App Router vs Pages Router confusion, incorrect exports, and deployment issues.
How to fix Next.js Module not found Can't resolve fs error caused by importing Node.js modules in client components, wrong server/client boundaries, and missing polyfills.
How to fix Node.js ERR_MODULE_NOT_FOUND when using ES modules, covering missing file extensions, directory imports, package.json exports, TypeScript paths, and ESM resolution differences.
How to fix the npm ENOENT no such file or directory error caused by missing package.json, wrong directory, corrupted node_modules, broken symlinks, and npm cache issues.
How to fix npm ERR code E404 not found error caused by typos, private registries, scoped packages, deleted packages, and authentication issues.
How to fix the npm ERR! Could not resolve peer dependency conflict error. Covers --legacy-peer-deps, --force, npm overrides, peerDependenciesMeta, React version conflicts, and debugging with npm ls.
npm WARN deprecated [email protected], [email protected], [email protected], @humanwhocodes — which warnings are safe to ignore, which need fixing, and exact steps to silence each one.
How to fix React TypeError Cannot read property map of undefined caused by uninitialized state, async data loading, wrong API response structure, and missing default values.
How to fix React Cannot update a component while rendering a different component caused by setState during render, context updates in render, and Redux dispatch in render.
How to fix the React unique key prop warning caused by missing keys in lists, duplicate keys, index keys, nested maps, and dynamic list rendering issues.
How to fix the React Invalid hook call error caused by mismatched React versions, duplicate React copies, calling hooks outside components, and class component usage.
How to fix the React error 'Objects are not valid as a React child' caused by rendering plain objects, Date objects, Promises, or API responses directly in JSX.
How to fix the React Hook useEffect has a missing dependency warning — covers the exhaustive-deps rule, useCallback, useMemo, refs, proper fetch patterns, and when to safely suppress the lint warning.
How to fix React useState not updating. Covers async state updates, functional updates, object mutations, stale closures, setTimeout issues, React 18 batching, props initialization, and debugging state changes.
How to fix TypeScript error TS2345 Argument of type is not assignable to parameter of type, covering null narrowing, union types, generics, callback types, type widening, enums, and React event handlers.
How to fix TypeScript Cannot find name error caused by missing type declarations, missing imports, wrong tsconfig settings, global types, and DOM API usage.
How to fix the TypeScript TS7016 error 'Could not find a declaration file for module' by installing @types packages, creating declaration files, and configuring tsconfig.json.
How to fix TypeScript error TS2339 'Property does not exist on type'. Covers missing interface properties, type narrowing, optional chaining, intersection types, index signatures, type assertions, type guards, window augmentation, and discriminated unions.
How to fix TypeScript strict null checks error Type X undefined is not assignable caused by optional values, nullable types, missing guards, and strictNullChecks.
How to fix the '[vite] server connection lost. Polling for restart...' error and HMR not working. Covers file watcher limits, WebSocket config, Docker polling, WSL2, proxy forwarding, SSL issues, firewall blocking, and dependency pre-bundling.
How to fix the Node.js digital envelope routines unsupported error caused by OpenSSL 3.0 changes in Node.js 17+, with solutions for webpack, Vite, React, and Angular.
How to fix Yarn integrity check failed and EINTEGRITY sha512 errors caused by corrupted cache, lock file mismatches, registry issues, and network problems.
How to fix the Yarn error 'integrity check failed' or 'Lockfile does not satisfy expected package' caused by corrupted cache, outdated lockfile, or version mismatches.
How to fix CORS errors when using cookies or Authorization headers, including 'Access-Control-Allow-Credentials' and wildcard origin conflicts.
How to fix Next.js Image component errors including 'Invalid src prop', 'hostname not configured', missing loader, and optimization failures in production.
How to fix the Webpack error 'Module not found: Error: Can't resolve' caused by missing packages, wrong paths, aliases, or extension resolution issues.
How to fix the React warning 'Can't perform a React state update on an unmounted component' caused by async operations, subscriptions, or timers.
How to fix VSCode's ESLint extension when it stops highlighting errors, shows no output, or fails to start. Covers flat config, settings, and common misconfigurations.
How to fix useEffect infinite loops in React — covers missing dependency arrays, referential equality, useCallback, unconditional setState, data fetching cleanup, event listeners, useRef, previous value comparison, and the exhaustive-deps lint rule.
How to fix ESLint 'Parsing error: Unexpected token' for JSX, TypeScript, and ES module syntax by configuring the correct parser, parserOptions, and ESLint config format.
How to fix 'Response to preflight request doesn't pass access control check' and 'preflight channel did not succeed' CORS errors by handling OPTIONS requests, setting correct headers, and configuring your server.
How to fix 'Module parse failed: Unexpected token' in Webpack, Vite, and esbuild by configuring the correct loaders and transforms for JSX, TypeScript, CSS, JSON, and other file types.
How to fix the Next.js hydration mismatch error. Covers invalid HTML nesting, browser extensions, Date/time differences, useEffect for client-only code, dynamic imports, suppressHydrationWarning, localStorage, third-party scripts, Math.random, auth state, and React portals.
How to fix TypeScript error TS2322 'Type is not assignable to type'. Covers literal types vs general types, string vs String, union types, interface compatibility, generic constraints, readonly arrays, excess property checking, discriminated unions, type assertions, type widening and narrowing, React event handlers, Promise return types, and enum mismatches.
How to fix 'Unexpected token in JSON at position 0', 'JSON.parse: unexpected character', and 'Unexpected end of JSON input' in JavaScript and TypeScript. Covers API returning HTML instead of JSON, Content-Type mismatches, fetch URL typos, invalid JSON syntax, BOM characters, CORS proxies, and debugging with response.text().
How to fix 'Loading chunk failed', 'ChunkLoadError', and 'Failed to fetch dynamically imported module' in webpack, Next.js, React, and Vite. Covers stale deployments, CDN caching, publicPath misconfiguration, service worker cache, code splitting, dynamic import retry strategies, React.lazy error boundaries, and Next.js-specific solutions.
How to fix TypeScript errors TS2532 'Object is possibly undefined', TS18048 'Object is possibly undefined', and 'Object is possibly null'. Covers optional chaining, nullish coalescing, type narrowing, non-null assertion, type guards, strictNullChecks, Array.find, Map.get, React useRef, and more.
How to fix 'Too many re-renders' in React. Covers calling functions in JSX instead of passing references, setState in the render body, useEffect infinite loops, object/array dependency issues, and how to debug re-renders with React DevTools.
How to fix 'Module not found: Can't resolve' in webpack, Vite, and React, and 'Cannot find module or its corresponding type declarations' in TypeScript. Covers missing packages, wrong import paths, case sensitivity, path aliases, node_modules corruption, monorepo hoisting, barrel files, and asset imports.
How to fix Vite's 'Failed to resolve import' error, including 'Does the file exist?', 'Optimized dependency needs to be force included', 'Pre-transform error', and '504 (Outdated Optimize Dep)'. Covers missing packages, path aliases, optimizeDeps, cache clearing, and CJS/monorepo edge cases.
How to fix 'React Hook is called conditionally', 'Rendered more hooks than during the previous render', 'Invalid hook call', and other React Hooks order errors. Covers conditional hooks, hooks in loops, hooks after early returns, duplicate React versions, and ESLint setup.
How to fix 'process.env.VARIABLE_NAME is undefined' and environment variables not loading from .env files in Node.js, React, Next.js, Vite, and Docker.
How to fix 'TypeError: Cannot read properties of undefined', 'Cannot read property of undefined', and 'Cannot read properties of null' in JavaScript, TypeScript, and React. Covers optional chaining, async data fetching, destructuring, and nested object access.
How to fix 'Error: Cannot find module' and 'MODULE_NOT_FOUND' in Node.js. Covers missing packages, wrong import paths, node_modules issues, TypeScript moduleResolution, ESM vs CJS, and monorepo hoisting.
How to fix 'Access to fetch at ... from origin ... has been blocked by CORS policy: No Access-Control-Allow-Origin header is present on the requested resource' in JavaScript. Covers Express, Django, Flask, Spring Boot, ASP.NET, nginx, Apache, dev proxies, preflight requests, credentials, and edge cases.