Error map
NG0100 Angular: NG0100: ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked
Angular · 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)
TS2564: Property 'x' has no initializer and is not definitely assigned in the constructor
With strictPropertyInitialization on, a class property declared without ? or a default isn’t set in the constructor.
Angular: NullInjectorError: No provider for X!
Angular’s dependency injection couldn’t find a provider for a service/token the component needs.
Angular: NG8002: Can't bind to 'ngModel' since it isn't a known property of 'input'
The template uses a property binding that no imported directive provides — for ngModel, FormsModule isn’t imported.
Angular: Error: Cannot find control with name: 'email' (reactive forms)
A `formControlName` points at a control that does not exist in the bound `FormGroup`.
Angular: NG0600: Writing to signals is not allowed in a computed or an effect by default
A `computed()` (or, by default, an `effect()`) tried to call `.set()` or `.update()` on a signal — that creates hidden update loo…
Angular: NG0955: The provided track expression resulted in duplicated keys for a given collection (@for)
In an `@for` block (or `trackBy`), two items produced the same tracking key, so Angular cannot match them to DOM nodes reliably.
Angular: TypeError: Cannot read properties of undefined (reading 'nativeElement') — @ViewChild used in ngOnInit
A `@ViewChild` / `viewChild()` reference is `undefined` because the view is not created yet, or the element sits inside `@if` / `…
Angular SSR: NG0500: During hydration Angular expected <div> but found <span> (NG0501, NG0502)
The HTML rendered on the server does not match what the browser's Angular app tried to render, so hydration failed and the page w…
Two steps away (23)
AttributeError: 'X' object has no attribute 'y'
You accessed an attribute or method that doesn’t exist on that object type.
java.lang.ClassCastException: class A cannot be cast to class B
An object was cast to a type it isn’t.
TypeError: x is not a constructor
new was used with something that isn’t a class/constructor — usually a wrong import.
InvalidOperationException: Unable to resolve service for type 'X' while attempting to activate 'Y'
ASP.NET Core’s dependency injection container can’t build Y because one of its constructor dependencies (X) was never registered.
UnsatisfiedDependencyException / NoSuchBeanDefinitionException: No qualifying bean of type 'X' available
Spring couldn’t find (or choose) a bean to inject.
The dependencies of some of the beans in the application context form a cycle
Two or more Spring beans depend on each other through constructors, and Spring Boot 2.6+ forbids cycles by default.
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.
django.template.exceptions.TemplateDoesNotExist: app/page.html
Django searched all template directories and couldn’t find that template.
Contact Form 7: There was an error trying to send your message. Please try again later.
The form submitted, but wp_mail() failed to send — the server can’t send mail or the mail settings are wrong.
Angular: NG8003: No directive found with exportAs 'ngForm' (template reference variable)
A template reference such as `#f="ngForm"` points at a directive Angular cannot find on that element — the module that provides i…
Angular: NG01203: No value accessor for form control with name: 'x' (ControlValueAccessor missing)
A form directive (`formControlName`, `ngModel`) is on an element or component that Angular cannot read/write values from.
Angular: NG01050: formControlName must be used with a parent formGroup directive
`formControlName` is used outside any `[formGroup]` — the control has no form to belong to.
Angular: NG0203: inject() must be called from an injection context such as a constructor, a factory function, a field initializer or a function used with runInInjectionContext
`inject()` was called somewhere Angular is not constructing a class — for example inside a method, a callback or after an `await`.
Angular build: Error: bundle initial exceeded maximum budget. Budget 1.00 MB was not met by 120.00 kB with a total of 1.12 MB
The production build is larger than the size limits (budgets) in angular.json, and the build is configured to fail.
Angular CLI: Schema validation failed with the following errors: Data path "" must NOT have additional properties(xyz)
`angular.json` (or an option you passed to a builder) contains a property the schema does not allow — a typo, an option removed i…
Angular: NG8103: The *ngIf directive was used, but neither the NgIf directive nor the CommonModule was imported
A standalone component uses `*ngIf`, `*ngFor` or `ngClass` without importing the directive — or should migrate to the built-in `@…
Angular: NG02200: Cannot find a differ supporting object '[object Object]' of type 'object'. NgFor only supports binding to Iterables such as Arrays
`*ngFor` (or `@for`) was given an object, `null` shape or a non-iterable instead of an array.
Angular CLI: Could not find the '@angular-devkit/build-angular:browser' builder's node package / Cannot find module '@angular-devkit/build-angular/package.json'
The build tooling package is missing from `node_modules` — dependencies were not installed or the lockfile/install is broken.
TypeError: Cannot read properties of null (reading 'addEventListener')
document.querySelector/getElementById returned null, so the element doesn’t exist when the script runs.
TypeError: Cannot read properties of undefined (reading 'length')
Code checked .length on something that is undefined — typically an array or string that hasn’t loaded.
Angular: NG0950: Input is required but no value is available yet (input.required / viewChild.required)
A required signal input or query was read before Angular set it — in the constructor or too early in the lifecycle.
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.
Angular SSR: ReferenceError: window is not defined / document is not defined / localStorage is not defined
Code that only works in a browser ran during server-side rendering, where `window`, `document` and `localStorage` do not exist.
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