angular keydown 例子

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 https://angular.cn/guide/observables keydown example

import { Component } from '@angular/core';
import { Observable, fromEvent } from 'rxjs';

@Component({
  selector: 'app-cust',
  template: `<p><button type="button" (click)="runExample()">{{title}}</button><input id="name" placeholder="type here"></p>`,
})
export class CustomersComponent {

  title = 'fromEvent - How to capture an event e.g. a keypress';

  runExample() {
    console.clear();

    // const myInput = document.getElementById('example-d');
    // const myObserverable = fromEvent(myInput, 'keyup');
    //
    // myObserverable
    //   .subscribe(
    //     value => console.log(value),
    //     err => console.error(err),
    //     () => console.log('Streaming is over')
    //   );

    function fromEvent(target, eventName) {
      return new Observable((observer) => {
        const handler = (e) => observer.next(e);

        // Add the event handler to the target
        target.addEventListener(eventName, handler);

        return () => {
          // Detach the event handler from the target
          target.removeEventListener(eventName, handler);
        };
      });
    }

    const ESC_KEY = 27;
    const nameInput = document.getElementById('name') as HTMLInputElement;

    const subscription = fromEvent(nameInput, 'keydown').subscribe((e: KeyboardEvent) => {
      if (e.keyCode === ESC_KEY) {
        nameInput.value = '';
      }
    });


  }
}