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React Errors

Complete guide to React framework errors and how to fix them.

14 Error Types
Cannot read property of undefined
Undefined Property Access

Trying to access a property on an undefined object, commonly occurs when data hasn't loaded yet.

Objects are not valid as a React child
Invalid React Child

Trying to render an object directly as a React child, which is not allowed.

Maximum update depth exceeded
Infinite Update Loop

Component is causing infinite re-renders, usually from setting state in render or useEffect without dependencies.

Warning: Each child in a list should have a unique key
Missing React Key

List items are missing unique 'key' props, which React needs for efficient rendering.

Hooks can only be called inside function components
Invalid Hook Usage

React hooks are being called outside of a function component or in the wrong order.

Rendered more hooks than during the previous render
Hook Order Changed

The number or order of hooks changed between renders, which violates React's rules of hooks.

Target container is not a DOM element
Invalid DOM Target

React is trying to render to a container that doesn't exist or isn't a valid DOM element.

Cannot update a component while rendering
State Update During Render

Trying to update component state during the render phase, which causes infinite loops.

useEffect has a missing dependency
Missing Dependency Warning

useEffect hook is missing dependencies in its dependency array, which can cause stale closures.

Text content does not match server-rendered HTML
Hydration Mismatch

The HTML rendered on the server doesn't match what React renders on the client, causing hydration errors.

Cannot read property 'map' of undefined
Undefined Array Access

Trying to call .map() on an undefined value, usually when data hasn't loaded yet.

Element type is invalid
Invalid Component

Trying to render an invalid React component, often from incorrect import or export.

Cannot find module
Module Import Error

React cannot find the imported module or component.

Invalid hook call
Hook Call Error

React hooks are being called incorrectly, outside component or in wrong context.