javascript - how do I debounce the @Output of an inner component?

Question

I have a component that wraps another component <inner-component> and binds to the InnerComponent.innerChanged() custom event. I want to bubble up using an @output property, but I also want to debounce the output.

How do I use RxJS .debounce() or .debounceTime() to do this?

Something like this:

import {Component, Output, EventEmitter} from 'angular2/core';
import 'rxjs/add/operator/debounce';
import 'rxjs/add/operator/debounceTime';

@Component({
  selector: 'debounced-component',
  template: `
    <div>
      <h1>Debounced Outer Component</h1>
      // export class InnerComponent{
      //   @Output() innerChanged: new EventEmitter<string>();
      //   onKeyUp(value){
      //     this.innerChanged.emit(value);
      //   }
      // }
      <input #inner type="text" (innerChange)="onInnerChange(inner.value)">
    </div>
  `
})
export class DebouncedComponent {
  @Output() outerValueChanged: new EventEmitter<string>();

  constructor() {}

  onInnerChange(value) {
    this.outerValuedChanged.emit(value); // I want to debounce() this.
  }
}

Answer 1

To debounce values you could use a Subject. A subject is both an observable and a observer. This means you can treat it as an observable and pass values to it as well.

You could leverage this to pass the new values from the inner-component to it and debounce it this way.

export class DebouncedComponent {
  @Output() outerValueChanged: new EventEmitter<string>();
  const debouncer: Subject<string> = new Subject<string>();

  constructor() {
      // you listen to values here which are debounced
      // on every value, you call the outer component
      debouncer
        .debounceTime(100)
        .subscribe((value) => this.outerValuedChanged.emit(value));
  }

  onInnerChange(value) {
    // send every value from the inner to the subject
    debouncer.next(value);
  }
}

This is untested pseudo-code. You can see a working example of the concept here (http://jsbin.com/bexiqeq/15/edit?js,console). It's without angular but the concept remains the same.

---

Update: For newer versions of Angular you might need a slight: change debouncer.debounceTime(100) gets changed to debouncer.pipe(debounceTime(100))

constructor() {
      // you listen to values here which are debounced
     // on every value, you call the outer component
     debouncer
       .pipe(debounceTime(100))
       .subscribe((value) => this.outerValuedChanged.emit(value));
}