Errors/React

Common React Errors

Common React errors including hooks violations, rendering loops, undefined property access, and component lifecycle issues.

60 errors documented with step-by-step fixes

Cannot read property of undefined React

Cannot read properties of undefined (reading 'map')

You tried to access a property on undefined, usually before data loads.

Too many re-renders React infinite loop

Too many re-renders

A state update triggers another render, creating an infinite loop.

React hooks rules violation

Rendered more hooks than during previous render

Hooks were called in a different order between renders.

Missing key prop React list

Each child in a list should have a unique key prop

List items rendered with map() are missing unique keys.

Maximum update depth exceeded React

Maximum update depth exceeded

useEffect with wrong dependencies causes infinite updates.

Cannot update component while rendering React

Cannot update a component while rendering

You set state in another component during render.

Hydration mismatch React Next.js

Hydration failed

Server HTML doesn't match client-rendered HTML.

Objects not valid React child

Objects are not valid as a React child

You tried to render a plain object instead of a string or JSX.

setState undefined React class

Cannot read property 'setState' of undefined

The this context is lost in a class component event handler.

useEffect cleanup React memory leak

useEffect cleanup function warning

An effect updates state after the component unmounts.

Invalid hook call React

Invalid hook call

Hooks can only be called inside function components.

Minified React error 301

Minified React error #301

A hooks-related error in production build.

Act warning React testing

Act warning in tests

State updates in tests need to be wrapped in act().

useRef null React

useRef current is null

The ref hasn't been attached to a DOM element yet.

Context undefined React

Context value is undefined

useContext returns undefined when the provider is missing.

React does not recognize the prop in React

Warning: React does not recognize the prop

This React error occurs when react does not recognize the prop. Check the stack trace for the exact location and fix the root cause.

Failed prop type in React

Warning: Failed prop type

This React error occurs when failed prop type. Check the stack trace for the exact location and fix the root cause.

Can't perform a React state update on an unmounted component in React

Warning: Can't perform a React state update on an unmounted component

This React error occurs when can't perform a react state update on an unmounted component. Check the stack trace for the exact location and fix the root cause.

Each child in a list should have a unique key prop in React

Warning: Each child in a list should have a unique key prop

This React error occurs when each child in a list should have a unique key prop. Check the stack trace for the exact location and fix the root cause.

Function components cannot be given refs in React

Warning: Function components cannot be given refs

This React error occurs when function components cannot be given refs. Check the stack trace for the exact location and fix the root cause.

Cannot update during an existing state transition in React

Warning: Cannot update during an existing state transition

This React error occurs when cannot update during an existing state transition. Check the stack trace for the exact location and fix the root cause.

Encountered two children with the same key in React

Warning: Encountered two children with the same key

This React error occurs when encountered two children with the same key. Check the stack trace for the exact location and fix the root cause.

Expected server HTML to contain a matching tag in React

Warning: Expected server HTML to contain a matching tag

This React error occurs when expected server html to contain a matching tag. Check the stack trace for the exact location and fix the root cause.

Did not expect server HTML to contain a element in React

Warning: Did not expect server HTML to contain a element

This React error occurs when did not expect server html to contain a element. Check the stack trace for the exact location and fix the root cause.

A component is changing an uncontrolled input to be controll in React

Warning: A component is changing an uncontrolled input to be controlled

This React error occurs when a component is changing an uncontrolled input to be controlled. Check the stack trace for the exact location and fix the root cause.

A component is changing a controlled input to be uncontrolle in React

Warning: A component is changing a controlled input to be uncontrolled

This React error occurs when a component is changing a controlled input to be uncontrolled. Check the stack trace for the exact location and fix the root cause.

validateDOMNesting: div cannot appear as descendant of p in React

Warning: validateDOMNesting: div cannot appear as descendant of p

This React error occurs when div cannot appear as descendant of p. Check the stack trace for the exact location and fix the root cause.

Suspense is not supported in Server Components in React

Error: Suspense is not supported in Server Components

This React error occurs when suspense is not supported in server components. Check the stack trace for the exact location and fix the root cause.

createContext is not supported in Server Components in React

Error: createContext is not supported in Server Components

This React error occurs when createcontext is not supported in server components. Check the stack trace for the exact location and fix the root cause.

Cannot read property 'current' of null (ref) in React

Error: Cannot read property 'current' of null (ref)

This React error occurs when cannot read property 'current' of null (ref). Check the stack trace for the exact location and fix the root cause.

Rendered fewer hooks than expected in React

Error: Rendered fewer hooks than expected

This React error occurs when rendered fewer hooks than expected. Check the stack trace for the exact location and fix the root cause.

React.createElement: type is invalid in React

Error: React.createElement: type is invalid

This React error occurs when type is invalid. Check the stack trace for the exact location and fix the root cause.

Element type is invalid: expected a string or class in React

Error: Element type is invalid: expected a string or class

This React error occurs when expected a string or class. Check the stack trace for the exact location and fix the root cause.

Nothing was returned from render in React

Error: Nothing was returned from render

This React error occurs when nothing was returned from render. Check the stack trace for the exact location and fix the root cause.

Adjacent JSX elements must be wrapped in enclosing tag in React

Error: Adjacent JSX elements must be wrapped in enclosing tag

This React error occurs when adjacent jsx elements must be wrapped in enclosing tag. Check the stack trace for the exact location and fix the root cause.

Unhandled Rejection in useEffect in React

Error: Unhandled Rejection in useEffect

This React error occurs when unhandled rejection in useeffect. Check the stack trace for the exact location and fix the root cause.

Cannot assign to 'current' because it is a read-only propert in React

Error: Cannot assign to 'current' because it is a read-only property

This React error occurs when cannot assign to 'current' because it is a read-only property. Check the stack trace for the exact location and fix the root cause.

Target container is not a DOM element in React

Error: Target container is not a DOM element

This React error occurs when target container is not a dom element. Check the stack trace for the exact location and fix the root cause.

ReactDOM.render is no longer supported in React 18 in React

Error: ReactDOM.render is no longer supported in React 18

This React error occurs when reactdom.render is no longer supported in react 18. Check the stack trace for the exact location and fix the root cause.

useNavigate() may only be used in context of Router in React

Error: useNavigate() may only be used in context of Router

This React error occurs when usenavigate() may only be used in context of router. Check the stack trace for the exact location and fix the root cause.

useLocation() may only be used in context of Router in React

Error: useLocation() may only be used in context of Router

This React error occurs when uselocation() may only be used in context of router. Check the stack trace for the exact location and fix the root cause.

Cannot read properties of null reading 'useState' in React

Error: Cannot read properties of null reading 'useState'

This React error occurs when cannot read properties of null reading 'usestate'. Check the stack trace for the exact location and fix the root cause.

Unexpected Application Error (React Router) in React

Error: Unexpected Application Error (React Router)

This React error occurs when unexpected application error (react router). Check the stack trace for the exact location and fix the root cause.

You cannot render a Router inside another Router in React

Error: You cannot render a Router inside another Router

This React error occurs when you cannot render a router inside another router. Check the stack trace for the exact location and fix the root cause.

No routes matched location in React

Error: No routes matched location

This React error occurs when no routes matched location. Check the stack trace for the exact location and fix the root cause.

useParams() may only be used in context of Router in React

Error: useParams() may only be used in context of Router

This React error occurs when useparams() may only be used in context of router. Check the stack trace for the exact location and fix the root cause.

Hydration failed because initial UI does not match in React

Error: Hydration failed because initial UI does not match

This React error occurs when hydration failed because initial ui does not match. Check the stack trace for the exact location and fix the root cause.

Text content did not match in React

Error: Text content did not match

This React error occurs when text content did not match. Check the stack trace for the exact location and fix the root cause.

There was an error while hydrating in React

Error: There was an error while hydrating

This React error occurs when there was an error while hydrating. Check the stack trace for the exact location and fix the root cause.

lazy() requires a promise-resolving module in React

Error: lazy() requires a promise-resolving module

This React error occurs when lazy() requires a promise-resolving module. Check the stack trace for the exact location and fix the root cause.

A component suspended while responding to synchronous input in React

Error: A component suspended while responding to synchronous input

This React error occurs when a component suspended while responding to synchronous input. Check the stack trace for the exact location and fix the root cause.

Missing queryClient (React Query) in React

Error: Missing queryClient (React Query)

This React error occurs when missing queryclient (react query). Check the stack trace for the exact location and fix the root cause.

No QueryClient set (TanStack Query) in React

Error: No QueryClient set (TanStack Query)

This React error occurs when no queryclient set (tanstack query). Check the stack trace for the exact location and fix the root cause.

Rendered more hooks than during previous render (variant) in React

Error: Rendered more hooks than during previous render (variant)

This React error occurs when rendered more hooks than during previous render (variant). Check the stack trace for the exact location and fix the root cause.

useFormContext must be used inside FormProvider in React

Error: useFormContext must be used inside FormProvider

This React error occurs when useformcontext must be used inside formprovider. Check the stack trace for the exact location and fix the root cause.

Cannot update a component from inside function body in React

Error: Cannot update a component from inside function body

This React error occurs when cannot update a component from inside function body. Check the stack trace for the exact location and fix the root cause.

findDOMNode is deprecated in StrictMode in React

Error: findDOMNode is deprecated in StrictMode

This React error occurs when finddomnode is deprecated in strictmode. Check the stack trace for the exact location and fix the root cause.

Portals must render into a DOM node in React

Error: Portals must render into a DOM node

This React error occurs when portals must render into a dom node. Check the stack trace for the exact location and fix the root cause.

React has detected a change in the order of Hooks in React

Error: React has detected a change in the order of Hooks

This React error occurs when react has detected a change in the order of hooks. Check the stack trace for the exact location and fix the root cause.

Maximum update depth exceeded (useEffect variant) in React

Error: Maximum update depth exceeded (useEffect variant)

This React error occurs when maximum update depth exceeded (useeffect variant). Check the stack trace for the exact location and fix the root cause.

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