Error map
[Vue warn]: Set operation on key failed: target is readonly Vue: [Vue warn]: Set operation on key "name" failed: target is readonly.
Vue · layer 1, On your device
Centre: this error. First ring: errors it is linked with (12). 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 (12)
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.
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.
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.
Vue: [Vue warn]: Missing required prop: "title"
A component marked a prop as `required` but the parent didn't pass it.
Vue: [Vue warn]: Maximum recursive updates exceeded in component <Foo>. This means you have a reactive effect that is mutating its own dependencies and thus recursively triggering itself
A watcher/computed/render effect keeps changing the state it depends on, creating an infinite update loop.
Vuex (strict mode): Error: [vuex] do not mutate vuex store state outside mutation handlers.
Store state was modified directly (in a component or action) while strict mode is on.
Next.js: Error: Failed prop type: The prop `href` expects a `string` or `object` in `<Link>`, but got `undefined` instead
`` received `undefined` (or another invalid value), so Next.js can't build the link.
Vue: [Vue warn]: Invalid prop: type check failed for prop "count". Expected Number with value 5, got String with value "5"
A prop received a value of the wrong type.
Vite/Vue: [plugin:vite:import-analysis] Failed to parse source for import analysis — you may need to install appropriate plugins to handle the .vue file format
Vite can't process `.vue` files because the Vue plugin isn't installed/enabled.
Vue: [Vue warn]: Write operation failed: computed value is readonly
You assigned to a `computed` that has no setter.
ESLint: Parsing error: Unexpected token < / Parsing error: '>' expected (vue-eslint-parser not configured)
ESLint can't parse `.vue` files because the Vue parser isn't configured.
Vue 2: [Vue warn]: Avoid adding reactive properties to a Vue instance or its root $data at runtime - declare it upfront in the data option
In Vue 2 you added a property to the root data (or instance) after creation, which can't be made reactive.
Two steps away (31)
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.
Warning: A component is changing an uncontrolled input to be controlled
An input’s `value` started as `undefined` (uncontrolled) and later became a defined value (controlled), or vice versa.
IndexError: list index out of range
Code accessed a list position that doesn’t exist.
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.
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.
Vue: [Vue warn]: Failed to resolve component: x
The template uses a component tag that isn’t registered or imported where it’s used.
Vue: [Vue warn]: Property "x" was accessed during render but is not defined on instance
The template references a variable/function that the component doesn’t expose.
TypeScript: error TS2741: Property 'email' is missing in type '{ name: string; }' but required in type 'User'.
An object lacks one required property of the target type.
TypeScript: error TS7031: Binding element 'name' implicitly has an 'any' type.
A destructured parameter has no type, so its elements default to `any`.
Vue: [Vue warn]: Extraneous non-props attributes (class) were passed to component but could not be automatically inherited because component renders fragment or text root nodes
Attributes (class, style, listeners) passed to a component can't be applied because the component has multiple root nodes.
Vue: [Vue warn]: Component emitted event "update" but it is neither declared in the emits option nor as an "onUpdate" prop
A component calls `emit("update")` without declaring it in `emits`.
Vue: [Vue warn]: Unhandled error during execution of mounted hook / TypeError: Cannot read properties of undefined (reading 'x')
An exception was thrown inside a lifecycle hook, watcher, event handler or render, and Vue logs it with the context.
Vue: [Vue warn]: Vue received a Component that was made a reactive object — mark it with `markRaw` or use `shallowRef`
A component definition was stored in a `ref`/`reactive`, making Vue proxy it unnecessarily.
Vue: [Vue warn]: Slot "default" invoked outside of the render function: this will not track dependencies used in the slot
A slot function was called outside render (in `setup`, a computed or watcher), so reactivity isn't tracked.
Vuex: [vuex] unknown mutation type: SET_USER / [vuex] unknown action type: fetchUser
`commit`/`dispatch` was called with a name that isn't registered in the store (or its module namespace).
Nuxt: [nuxt] error caught during app initialization TypeError: Failed to fetch dynamically imported module / Loading chunk failed
A browser tab running the old build requests chunk files that were replaced by a new deployment.
Nuxt: 404 Page not found: /blog/my-post / [Vue Router warn]: No match found for location with path
Nuxt's file-based router has no page matching the URL (wrong file/folder names or missing param syntax).
You're importing a component that needs useState. It only works in a Client Component but none of its parents are marked with "use client"
In the Next.js App Router, a component using hooks or browser APIs is rendered as a Server Component.
Next.js: FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory (during next build)
Node ran out of memory while building a large Next.js app (or on a small CI/Vercel runner).
Next.js: Error occurred prerendering page "/blog" TypeError: fetch failed { cause: Error: connect ECONNREFUSED 127.0.0.1:3000 }
During `next build` a page tried to fetch data from a server (often your own app or an API) that isn't running yet.
Vue: [Vue warn]: injection "theme" not found.
`inject("theme")` ran but no ancestor provided it.
Vue: [Vue warn]: The computed property "name" is already defined in data.
A name is used twice among props/data/computed/methods in the Options API.
[vite] Internal server error: Failed to resolve import "x" from "src/App.jsx". Does the file exist?
Vite couldn’t find an imported file or package.
[vite] hmr invalidate … Could not Fast Refresh. Export is incompatible.
Fast Refresh fell back to a full reload because the file exports non-components alongside components.
Vue: [Vue warn]: Duplicate keys found during update: "5", possible duplicate or missing keys
Items in a `v-for` list share the same `:key`, which breaks Vue's diffing.
Vue: [@vue/compiler-sfc] v-model cannot be used on a prop, because local prop bindings are not writable
A template uses `v-model` on a prop (or a `v-for` alias), which can't be assigned.
React Hook useEffect has a missing dependency (react-hooks/exhaustive-deps)
ESLint warns that the effect reads a value that isn’t in its dependency array, so it may use a stale value.
Next.js: Failed to compile. ./src/app/page.tsx 12:7 Error: 'x' is assigned a value but never used. @typescript-eslint/no-unused-vars
`next build` runs ESLint and fails the build on lint errors.
TypeScript: error TS1005: ';' expected.
The parser hit a syntax error — missing punctuation, mismatched brackets, or an unsupported syntax for your TypeScript version.
Vue 2: [Vue warn]: Error in v-on handler: "TypeError: Cannot read property 'x' of undefined"
An exception was thrown inside a Vue 2 event handler or lifecycle hook, logged with context.
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