Error map
Invalid DOM property Warning: Invalid DOM property `class`. Did you mean `className`?
React · layer 1, On your device
Centre: this error. First ring: errors it is linked with (8). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (8)
Warning: Functions are not valid as a React child. This may happen if you return a Component instead of <Component /> from render.
A function (usually a component itself) was rendered instead of calling/rendering it as an element.
Error: Objects are not valid as a React child
You tried to render a plain object (or a Promise/Date) directly in JSX; React can only render strings, numbers, elements and arra…
Error: Nothing was returned from render. This usually means a return statement is missing.
A component returned undefined (React 17 and earlier) — usually a missing return or a return followed by a line break.
DOMException: Failed to execute 'querySelector' on 'Document': 'x' is not a valid selector
The CSS selector string is invalid — often an ID starting with a digit or containing special characters.
Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>?
A component returns two sibling JSX elements without a single parent.
ReferenceError: React is not defined / 'React' must be in scope when using JSX
JSX was compiled with the classic runtime, which needs React imported in every file.
Warning: Received `true` for a non-boolean attribute `x`.
A boolean was passed to a DOM attribute that expects a string, or a custom prop leaked through to a DOM element.
Error: createRoot(...): Target container is not a DOM element.
The element passed to createRoot/render doesn’t exist when the script runs.
Two steps away (21)
Error: Too many re-renders. React limits the number of renders to prevent an infinite loop.
A state update runs during render, which triggers another render, which updates state again — forever.
Warning: Each child in a list should have a unique "key" prop
When rendering a list with `.map()`, each element needs a stable, unique `key` so React can track items between renders.
Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined
JSX referenced a component that is undefined — almost always a default/named import mismatch.
TypeError: Cannot read properties of undefined (reading 'x')
You tried to access a property on a value that is `undefined` (or `null`) — usually data that hasn’t loaded yet or a wrong proper…
Error: Hydration failed because the initial UI does not match what was rendered on the server
The HTML rendered on the server differs from the first client render, so React (Next.js/Remix) can’t attach to it.
Error: A component suspended while responding to synchronous input.
A component suspended (lazy load or data fetch) during an update that wasn’t wrapped in a transition, and there is no Suspense bo…
Warning: Cannot update a component (`Parent`) while rendering a different component (`Child`)
A child component updated a parent’s state during its render instead of in an effect or event handler.
TypeError: Cannot read properties of null (reading 'addEventListener')
document.querySelector/getElementById returned null, so the element doesn’t exist when the script runs.
ResizeObserver loop completed with undelivered notifications.
A ResizeObserver callback changed layout in a way that triggered another resize in the same frame.
AbortError: The user aborted a request. / signal is aborted without reason
A fetch was cancelled through an AbortController (or the browser cancelled it).
SyntaxError: Invalid regular expression: /x/: Unterminated group
A regex pattern has invalid syntax — unbalanced parentheses/brackets or unescaped special characters.
Warning: validateDOMNesting(...): <div> cannot appear as a descendant of <p>.
The JSX produces invalid HTML nesting, which also causes hydration mismatches in SSR.
Error: useNavigate() may be used only in the context of a <Router> component.
A React Router hook ran in a component that isn’t rendered inside a Router provider.
ReferenceError: x is not defined
Code refers to a variable or function name that doesn’t exist in the current scope.
API Error: Invalid or unsupported API version
The API version you requested — in the URL, a header or the SDK config — doesn’t exist or has been retired.
API Error: Feature not enabled for this account (feature_not_enabled / not available on your plan)
The endpoint or option exists, but your account, plan, region or project hasn’t been granted access to it.
Warning: `key` is not a prop. Trying to access it will result in `undefined` being returned.
A component tried to read props.key, which React reserves and never passes down.
Vue: [Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders
A child component assigned to a prop. Props flow one way — the parent owns the value.
fatal: not a git repository (or any of the parent directories): .git
You ran a Git command outside a Git working tree.
Author identity unknown *** Please tell me who you are.
Git doesn’t know your name and email for commits.
ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
Build tools (Gradle, Maven, Android tools) can’t find a JDK.
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