Countdown

components.my-countdown.js

import Ember from 'ember';
import { computed } from '@ember/object';
import { task, timeout } from 'ember-concurrency';

export default Ember.Component.extend({

  startValue: 10,
  currentValue: null,

  init() {
    this._super(...arguments);
    this.set('currentValue', this.get('startValue'));
  },
  
  countdownTask: task(function * () {
    while (! this.get('countdownFinished')) {
      this.decrementProperty('currentValue');
      yield timeout(1000);
    }
  }),
    
  countdownFinished: computed('currentValue', function () {
    return this.get('currentValue') <= 0;
  }),
  
});

templates.application.hbs

{{my-countdown}}

templates.components.my-countdown.hbs

<h2>Countdown: {{this.currentValue}}</h2>

{{#if this.countdownTask.isIdle}}
  <button onclick={{action (perform this.countdownTask)}}>Start</button>
{{else}}
  <button onclick={{action (cancel-all this.countdownTask)}}>Stop</button>
{{/if}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-concurrency": "1.0.0",
    "ember-data": "3.4.2"
  }
}