All Errors

This error occurs when an asynchronous operation takes longer than the specified timeout duration to complete. The promise remains in a pending state past its deadline, triggering a timeout rejection to prevent indefinite waiting.

HTTP 429 Too Many Requests indicates your Node.js application has exceeded the API rate limit. The server is asking your client to slow down request frequency.

This warning occurs when a Promise is rejected but no error handler catches the rejection. Starting from Node.js 15, unhandled promise rejections cause the application to terminate, making proper error handling critical for application stability.

This error occurs when attempting to send a message through a MessagePort that has already been closed or whose worker thread has terminated. The communication channel between the main thread and worker is no longer available.

React throws this error when useDeferredValue is called inside a conditional statement, loop, or nested function. All hooks must be called in the same order on every render to maintain state consistency.

This error occurs when you try to define a Client Component as an async function in React or Next.js. Client Components do not support async functions because they run in the browser where async component rendering is not yet supported. Only Server Components can be async, allowing them to await data directly in the component body.

This error occurs when mixing getInitialProps (often in _app.js) with getStaticProps in page components. Next.js prevents this combination because getInitialProps disables automatic static optimization and conflicts with build-time static generation.

This error occurs when trying to use class field syntax to initialize state without proper Babel configuration, or when the build tool doesn't support class properties. The state property must be assigned in the constructor using `this.state = {}` or class properties transform must be enabled.

The "Unexpected token ) in JSON" error occurs when your React application attempts to parse invalid JSON data. This typically happens when fetching data from an API and trying to parse the response, but the response is not valid JSON—often containing extra characters, syntax errors, or non-JSON content like HTML error pages.

This error occurs when attempting to access AsyncLocalStorage data outside of an asynchronous context initialized by run() or enterWith(). The store is only available within the callback scope or in operations properly bound to that context.

This webpack error occurs when files containing JSX, special syntax, or binary content are processed without the appropriate loader configured. The bundler attempts to parse the file as plain JavaScript but encounters characters it cannot understand.

This warning occurs when React attempts to update or interact with a component that has already been unmounted from the DOM. It typically happens when asynchronous operations like timers, API calls, or event listeners complete after the component has been removed, causing memory leaks and potential crashes.

This error occurs when React is not properly imported or in scope when JSX is used. It commonly happens due to missing import statements, incorrect bundler configuration, or issues with the React 17+ JSX transform.

This error occurs when attempting to render a plain JavaScript object directly in JSX. React requires you to render primitives, elements, or arrays, not raw objects.

This warning appears during React hydration when the className generated on the server differs from the one generated on the client. Commonly caused by CSS-in-JS libraries like styled-components, Material-UI, or conditional rendering that differs between server and client.

React event handlers may fail to prevent default behavior when preventDefault() is called incorrectly or when accessing synthetic events asynchronously. This commonly occurs when functions are invoked instead of passed as references, or when trying to access event properties in async callbacks.

This error occurs when a React component returns an invalid value like undefined, typically due to a missing return statement. In React versions before 18, components that returned undefined or false would throw this error, though React 18+ is more lenient with undefined returns.

This ESLint warning occurs when your useEffect hook references variables, props, or state that are not included in its dependency array. When dependencies are missing, your effect may run with stale values or fail to re-run when those values change, leading to bugs and unexpected behavior.

JSX syntax errors occur when React encounters improperly formatted HTML-like code that violates JSX rules. These errors commonly arise from unclosed tags, missing parent wrappers, or using HTML syntax instead of JSX conventions.

This error occurs when attempting to decode a base64 string that has incorrect padding. Base64 encoding requires padding to a multiple of 4 characters using the "=" character, and improper padding causes decoding failures in strict validation contexts.