angular-cn/aio/content/examples/rx-library/src/naming-convention.ts

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

@Component({
  selector: 'app-stopwatch',
  templateUrl: './stopwatch.component.html'
})
export class StopwatchComponent {

  stopwatchValue: number;
  stopwatchValue$: Observable<number>;

  start() {
    this.stopwatchValue$.subscribe(num =>
      this.stopwatchValue = num
    );
  }
}