countdown timer

components.my-component\.js

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { action } from '@ember/object';
import { later } from '@ember/runloop';

export default class extends Component {
  @tracked startTime = 5;
  @tracked isCounting = false;

  @action
  startCountdown() {
    this.isCounting = true;
    this.startTime = this.startTime - 1;

    if (this.startTime <= 0) {
      this.startTime = 5;
      this.isCounting = false;
      return;
    }

    later(this, this.startCountdown, 1000);
  }
}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
<MyComponent />
<br>
<br>

templates.components.my-component\.hbs

<p>Click start to begin count down</p>

<Input type="number" @value={{this.startTime}} readonly={{this.isCounting}} />
<button {{on 'click' this.startCountdown}} disabled={{this.isCounting}}>Start</button>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}