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Angular provides two interop helpers for opposite directions: outputFromObservable() exposes an RxJS stream as a component or directive output, while outputToObservable() converts an Angular output into an RxJS Observable. For a new imperative event, use output(). These function-based APIs are intended for Angular v19 and later; check the documentation for your installed release before adopting them.
Choose the API by the direction of the event
| Need | Use | What it does |
|---|---|---|
| Emit an event when component code decides | output() |
Declares an Angular output that component code emits with .emit(). |
| Expose an existing RxJS stream as an Angular output | outputFromObservable(source$) |
Forwards values from an Observable to consumers of the component or directive output. |
| Use an Angular output in an RxJS pipeline | outputToObservable(outputRef) |
Adapts an output to an RxJS Observable for operators and composition. |
| Listen to an output with a callback only | OutputRef.subscribe() |
Subscribes directly, without adding an RxJS conversion when no pipeline is needed. |
Angular documents output() as stable since v19.0. Its function-based output API is recommended for new projects, but the older @Output() and EventEmitter approach remains supported. See Angular’s component outputs guide and output() API reference.
Declare an output for imperative events
Use output() when the component itself determines when an event occurs. It returns an OutputEmitterRef, which exposes .emit(). Declare it as a class property initializer in a component or directive; Angular recognizes this initializer as an output declaration.
import { Component, output } from '@angular/core';
@Component({
selector: 'app-save-button',
template: '<button (click)="save()">Save</button>',
})
export class SaveButtonComponent {
saved = output<string>();
save() {
this.saved.emit('done');
}
}A parent can listen with a template binding such as <app-save-button (saved)="handleSaved($event)" />. Angular also supports programmatic subscription to an output reference. Angular cleans up output subscriptions when it destroys the component.
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Expose an Observable as an Angular output
Use outputFromObservable() when an RxJS Observable already represents the event stream and consumers should receive it through the component’s normal output interface. Declare the interop call as a property initializer in the component or directive.
import { Component, outputFromObservable } from '@angular/core';
import { fromEvent } from 'rxjs';
@Component({
selector: 'app-pointer-tracker',
template: '<div class="area">Move the pointer here</div>',
})
export class PointerTrackerComponent {
private pointerMoves$ = fromEvent<PointerEvent>(window, 'pointermove');
pointerMove = outputFromObservable(this.pointerMoves$);
}The output forwards Observable values to output subscribers. Forwarding stops when the owning component or directive is destroyed. If the source completes, no further values are forwarded. Angular does not handle errors from the source Observable for you: arrange error handling in the stream or otherwise manage the error yourself. See Angular’s outputFromObservable() API reference.
Convert an Angular output to an Observable
Use outputToObservable() when you need to pass values from an Angular output through RxJS operators. The helper returns an Observable<T>.
import { Component, output, outputToObservable } from '@angular/core';
import { debounceTime } from 'rxjs';
@Component({
selector: 'app-search-box',
template: '<input (input)="queryChange.emit($any($event.target).value)">',
})
export class SearchBoxComponent {
queryChange = output<string>();
debouncedQuery$ = outputToObservable(this.queryChange).pipe(debounceTime(250));
}This is useful when an output needs RxJS composition, such as filtering or combining streams. If the task is only to run a callback when the output emits, use OutputRef.subscribe() instead. Angular ties subscriptions made through the interop helper to the component or directive owner’s destruction. See the outputToObservable() API reference.
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Keep or migrate legacy EventEmitter outputs
EventEmitter<T> is the decorator-era event mechanism and extends RxJS Subject<T>, adding .emit(). Existing code using @Output() and EventEmitter can continue to work; there is no need to convert a component solely because the function-based API is newer. For new declarations, Angular recommends output(). The Angular outputs guide describes both approaches.
To migrate eligible declarations, run the Angular CLI schematic:
ng generate @angular/core:output-migrationThe schematic can update eligible output members and imports, change certain .next() calls to .emit(), and remove .complete() calls. It does not cover every code shape.
- It may skip output usages involving
.pipe()outside recognized test files. For test files, its documented recognition looks for imports containingjasmineorcatalyst; some piped test usages may be rewritten tooutputToObservable(...). --pathlimits which files are changed.--analysis-dirlimits reference analysis; if references lie outside that directory, they can be missed and the migration may break the build.- Review the generated diff and run the project’s tests and build after migration.
See Angular’s output migration guide for the schematic’s behavior and options.
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Angular outputs are custom component events, not bubbling DOM events. A listener on an ancestor element will not receive an output emitted by a nested component unless the component hierarchy explicitly passes it along. Output names are case-sensitive.
- An alias changes the public name used in a template, not the TypeScript property name.
- Outputs inherited from a base component are also available on child classes.
- Use camelCase, avoid an
onprefix, and avoid names that collide with native DOM events.
These naming and binding rules are described in the Angular component outputs guide.
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