html - How to start timer only for selected item ? Angular Javascript

Question

First look at my code which is complete here:

https://stackblitz.com/edit/test-trainin-2-gv9glh?file=src%2Fapp%2Fapp.component.html

When you press the 'Go' button you will see a timer that starts counting the seconds. I just want to click Go to count the seconds to click the row - card. Check function:

  startTimerForSingleTraining(j) {
    this.selectedTrainingIndex = this.selectedTrainingIndex === j ? null : j;
    // selectedTrainingIndex
    console.log(j);
    this.countDownForSingleStartTraining = timer(0, this.tick).subscribe(
      () => ++this.counterForSingleTrainingStart
    );
  }

and in html:

    <div class="button-absolute-page">
      <button
      class="btn btn-primary"
      (click)="finishedTraining(training)"
       (click)="startTimerForSingleTraining(j)"
       >
        Go
    </button>
   </div>

Answer 1

等待大神解答