New Twiddle

components.programming-languages.js

import Ember from 'ember';
import { inject } from '@ember/service';
import { computed } from '@ember/object';

export default Ember.Component.extend({
  modeService: inject(),
  renderList: computed('modeService.mode', function(){
    let mode = this.get('modeService.mode');
    return mode === 'list';
  })
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  init(){
    this._super(...arguments);
    this.set('languages', [
      'javascript', 'swift', 'groovy', 'haskell' 
    ]);
  }
});

mode-changer.component.js

import Ember from 'ember';
import { inject } from '@ember/service';
import { computed } from '@ember/object';

export default Ember.Component.extend({
  modeService: inject(),
  buttonText: computed('modeService.mode', function(){
    let mode = this.get('modeService.mode');
    return mode === 'list' ? "Change to table" : "Change to list";
  }),
  actions: {
    toggleMode(){
      let modeService = this.get('modeService');
      modeService.toggleMode();
    }
  }
});

mode-changer.template.hbs

<button onclick={{action 'toggleMode'}}>{{buttonText}}</button>

services.mode-service.js

import Ember from 'ember';

export default Ember.Service.extend({
  init(){
    this._super(...arguments);
    //actually read from local storage here and set default on null
    this.set('mode', 'list');
  },
  toggleMode(){
    let newValue = this.get('mode') === 'list' ? 'table' : 'list';
    //actually store to local storage here before caching on the service
    this.set('mode', newValue);  
  }
});

templates.application.hbs

<h1>Choose your mode</h1>
<br>
<br>
{{programming-languages languages=languages}}
{{mode-changer}}
<br>
<br>

templates.components.programming-languages.hbs

{{#if renderList}}
	<ol>
  {{#each languages as |language|}}
    <li>{{language}}</li>
  {{/each}}
  </ol>
{{else}}
  <table>
  	<th>Language</th>
	  {{#each languages as |language|}}
      <tr>{{language}}</tr>
    {{/each}}
  </table>
{{/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-data": "3.4.2"
  }
}