Error map

[Vue warn]: Invalid prop: type check failed Vue: [Vue warn]: Invalid prop: type check failed for prop "count". Expected Number with value 5, got String with value "5"

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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.

[Vue warn]: Invalid prop: type check failed — Vue: [Vue warn]: Invalid prop: type check failed for prop "count". Expected Number with value 5, got String with value "5" (Vue)[Vue warn]:…key is not a prop — Warning: `key` is not a prop. Trying to access it will result in `undefined` being returned. (React)key is not a propnon-boolean attribute — Warning: Received `true` for a non-boolean attribute `x`. (React)non-boolean attribu…Avoid mutating a prop directly — Vue: [Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders (Vue)Avoid mutating a pr…TS2741: Property is missing in type but required in type — TypeScript: error TS2741: Property 'email' is missing in type '{ name: string; }' but required in type 'User'. (TypeScript)TS2741: Property is…[Vue warn]: Extraneous non-props attributes — 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 (Vue)[Vue warn]: Extrane…[Vue warn]: Missing required prop — Vue: [Vue warn]: Missing required prop: "title" (Vue)[Vue warn]: Missing…[Vue warn]: Set operation on key failed: target is readonly — Vue: [Vue warn]: Set operation on key "name" failed: target is readonly. (Vue)[Vue warn]: Set ope…Failed prop type: The prop href expects a string or object in <Link> — Next.js: Error: Failed prop type: The prop `href` expects a `string` or `object` in `<Link>`, but got `undefined` instead (Next.js)Failed prop type: T…[Vue warn]: injection "x" not found — Vue: [Vue warn]: injection "theme" not found. (Vue)[Vue warn]: injecti…TS7031: Binding element implicitly has an 'any' type — TypeScript: error TS7031: Binding element 'name' implicitly has an 'any' type. (TypeScript)TS7031: Binding ele…[Vue warn]: Component emitted event but it is neither declared in the emits option nor as an onXxx prop — Vue: [Vue warn]: Component emitted event "update" but it is neither declared in the emits option nor as an "onUpdate" prop (Vue)[Vue warn]: Compone…Vite: Failed to parse source / Unknown file extension ".vue" — 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 (Vue)Vite: Failed to par…unique key prop — Warning: Each child in a list should have a unique "key" prop (React)unique key propuncontrolled to controlled — Warning: A component is changing an uncontrolled input to be controlled (React)uncontrolled to con…IndexError — IndexError: list index out of range (Python)IndexErrorObjects are not valid as a React child — Error: Objects are not valid as a React child (React)Objects are not val…Nothing was returned from render — Error: Nothing was returned from render. This usually means a return statement is missing. (React)Nothing was returne…Adjacent JSX elements — Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>? (React)Adjacent JSX elemen…Failed to resolve component — Vue: [Vue warn]: Failed to resolve component: x (Vue)Failed to resolve c…Property was accessed during render but is not defined — Vue: [Vue warn]: Property "x" was accessed during render but is not defined on instance (Vue)Property was access…[Vue warn]: Duplicate keys found during update — Vue: [Vue warn]: Duplicate keys found during update: "5", possible duplicate or missing keys (Vue)[Vue warn]: Duplica…TS2339 — TS2339: Property 'x' does not exist on type 'Y'. (Node.js)TS2339TS2551: Property does not exist. Did you mean — TypeScript: error TS2551: Property 'lenght' does not exist on type 'string'. Did you mean 'length'? (TypeScript)TS2551: Property do…TS2353: Object literal may only specify known properties — TypeScript: error TS2353: Object literal may only specify known properties, and 'nmae' does not exist in type 'User' (TypeScript)TS2353: Object lite…ESLint Parsing error in .vue files — ESLint: Parsing error: Unexpected token < / Parsing error: '>' expected (vue-eslint-parser not configured) (Vue)ESLint Parsing erro…[Vue warn]: <TransitionGroup> children must be keyed — Vue: [Vue warn]: <TransitionGroup> children must be keyed: <li> (Vue)[Vue warn]: <Transi…[Vue warn]: Maximum recursive updates exceeded — 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 (Vue)[Vue warn]: Maximum…[Vue warn]: Write operation failed: computed value is readonly — Vue: [Vue warn]: Write operation failed: computed value is readonly (Vue)[Vue warn]: Write o…Error: [vuex] do not mutate vuex store state outside mutation handlers — Vuex (strict mode): Error: [vuex] do not mutate vuex store state outside mutation handlers. (Vue)Error: [vuex] do no…needs useState — 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" (React)needs useStatenext build: JavaScript heap out of memory — Next.js: FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory (during next build) (Next.js)next build: JavaScr…next build: fetch failed ECONNREFUSED (build-time API) — Next.js: Error occurred prerendering page "/blog" TypeError: fetch failed { cause: Error: connect ECONNREFUSED 127.0.0.1:3000 } (Next.js)next build: fetch f…[Vue warn]: onMounted is called when there is no active component instance — Vue: [Vue warn]: onMounted is called when there is no active component instance to be associated with (Vue)[Vue warn]: onMount…injection "Symbol(router)" not found / useRouter() called without router — Vue Router: [Vue warn]: injection "Symbol(router)" not found. / Cannot read properties of undefined (reading 'push') (Vue)injection "Symbol(r…[Vue warn]: Failed to locate Teleport target with selector — Vue: [Vue warn]: Failed to locate Teleport target with selector "#modal". Note the target element must exist before the component is mounted (Vue)[Vue warn]: Failed …TS7006 — TS7006: Parameter 'x' implicitly has an 'any' type (TypeScript)TS7006TS7005: Variable implicitly has an 'any' type — TypeScript: error TS7005: Variable 'x' implicitly has an 'any[]' type. / TS7034: Variable implicitly has type 'any' in some locations (TypeScript)TS7005: Variable im…TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to index — TypeScript: error TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ a: number; }' (TypeScript)TS7053: Element imp…v-model cannot be used on a prop (compile error) — Vue: [@vue/compiler-sfc] v-model cannot be used on a prop, because local prop bindings are not writable (Vue)v-model cannot be u…Vite failed to resolve import — [vite] Internal server error: Failed to resolve import "x" from "src/App.jsx". Does the file exist? (React)Vite failed to reso…Could not Fast Refresh — [vite] hmr invalidate … Could not Fast Refresh. Export is incompatible. (React)Could not Fast Refr…[Vue warn]: Hydration node/text/children mismatch — Vue: [Vue warn]: Hydration text content mismatch / Hydration node mismatch: server rendered element contains more child nodes than client vdom (Vue)[Vue warn]: Hydrati…

Directly related (12)

key is not a propReact

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.

non-boolean attributeReact

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.

Avoid mutating a prop directlyVue

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.

TS2741: Property is missing in type but required in typeTypeScript

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.

[Vue warn]: Extraneous non-props attributesVue

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 warn]: Missing required propVue

Vue: [Vue warn]: Missing required prop: "title"

A component marked a prop as `required` but the parent didn't pass it.

[Vue warn]: Set operation on key failed: target is readonlyVue

Vue: [Vue warn]: Set operation on key "name" failed: target is readonly.

You mutated a readonly reactive object (props, `readonly()`, `shallowReadonly`, or a frozen/store state).

Failed prop type: The prop href expects a string or object in <Link>Next.js

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 warn]: injection "x" not foundVue

Vue: [Vue warn]: injection "theme" not found.

`inject("theme")` ran but no ancestor provided it.

TS7031: Binding element implicitly has an 'any' typeTypeScript

TypeScript: error TS7031: Binding element 'name' implicitly has an 'any' type.

A destructured parameter has no type, so its elements default to `any`.

[Vue warn]: Component emitted event but it is neither declared in the emits option nor as an onXxx propVue

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`.

Vite: Failed to parse source / Unknown file extension ".vue"Vue

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.

Two steps away (30)

unique key propReact

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.

uncontrolled to controlledReact

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.

IndexErrorPython

IndexError: list index out of range

Code accessed a list position that doesn’t exist.

Objects are not valid as a React childReact

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…

Nothing was returned from renderReact

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 elementsReact

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.

Failed to resolve componentVue

Vue: [Vue warn]: Failed to resolve component: x

The template uses a component tag that isn’t registered or imported where it’s used.

Property was accessed during render but is not definedVue

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.

[Vue warn]: Duplicate keys found during updateVue

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.

TS2339Node.js

TS2339: Property 'x' does not exist on type 'Y'.

TypeScript’s type for the object doesn’t include that property.

TS2551: Property does not exist. Did you meanTypeScript

TypeScript: error TS2551: Property 'lenght' does not exist on type 'string'. Did you mean 'length'?

A property name is misspelled (TypeScript suggests the closest valid one).

TS2353: Object literal may only specify known propertiesTypeScript

TypeScript: error TS2353: Object literal may only specify known properties, and 'nmae' does not exist in type 'User'

An object literal has an extra (or misspelled) property not in the target type (excess property check).

ESLint Parsing error in .vue filesVue

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 warn]: <TransitionGroup> children must be keyedVue

Vue: [Vue warn]: <TransitionGroup> children must be keyed: <li>

Children of `` lack a unique `key`, so animations can't track items.

[Vue warn]: Maximum recursive updates exceededVue

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.

[Vue warn]: Write operation failed: computed value is readonlyVue

Vue: [Vue warn]: Write operation failed: computed value is readonly

You assigned to a `computed` that has no setter.

Error: [vuex] do not mutate vuex store state outside mutation handlersVue

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.

needs useStateReact

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 build: JavaScript heap out of memoryNext.js

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 build: fetch failed ECONNREFUSED (build-time API)Next.js

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 warn]: onMounted is called when there is no active component instanceVue

Vue: [Vue warn]: onMounted is called when there is no active component instance to be associated with

A lifecycle hook was registered outside `setup()` (or after an `await`).

injection "Symbol(router)" not found / useRouter() called without routerVue

Vue Router: [Vue warn]: injection "Symbol(router)" not found. / Cannot read properties of undefined (reading 'push')

`useRouter()`/`useRoute()` ran in a component tree where the router plugin isn't installed.

[Vue warn]: Failed to locate Teleport target with selectorVue

Vue: [Vue warn]: Failed to locate Teleport target with selector "#modal". Note the target element must exist before the component is mounted

`` can't find its target element when mounting.

TS7006TypeScript

TS7006: Parameter 'x' implicitly has an 'any' type

A function parameter has no type annotation and TypeScript can’t infer one, which noImplicitAny (part of strict) forbids.

TS7005: Variable implicitly has an 'any' typeTypeScript

TypeScript: error TS7005: Variable 'x' implicitly has an 'any[]' type. / TS7034: Variable implicitly has type 'any' in some locations

With `noImplicitAny`, a variable's type can't be inferred and defaults to `any`.

TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to indexTypeScript

TypeScript: error TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ a: number; }'

You index an object with a general `string` key, but its type only knows specific keys.

v-model cannot be used on a prop (compile error)Vue

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.

Vite failed to resolve importReact

[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.

Could not Fast RefreshReact

[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 warn]: Hydration node/text/children mismatchVue

Vue: [Vue warn]: Hydration text content mismatch / Hydration node mismatch: server rendered element contains more child nodes than client vdom

Server-rendered HTML differs from what the client renders on first load.