Conditional Yield

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

controllers.index.js

import Ember from 'ember';
import { task, timeout } from 'ember-concurrency';

export default Ember.Controller.extend({
  myTask: task(function * () {
    let tmp = false;
    yield timeout(200);
    if (tmp) {
      yield timeout(200);
      alert('is true');
    } else {
      alert('is false');
    }
  }),
  
  actions: {
    runTask() {
      this.get('myTask').perform();
    }
  }
});

routes.index.js

import Ember from 'ember';

export default Ember.Route.extend({
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

templates.index.hbs

<button {{action 'runTask'}}>Click</button>

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-data": "3.4.2",
    "ember-concurrency": "latest"
  }
}