Demonstrate multiple select

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  optionDefaults: Ember.computed(function() {
  	return ['foofoo', 'barbar', 'bazbaz'];
  }),
  
  optionsSelected: Ember.computed(function() {
  	return [];
  }),
  
  selectOptions: Ember.computed('optionsSelected', function() {
  	const optionsSelected = this.get('optionsSelected');
    const optionDefaults = this.get('optionDefaults');

    return optionDefaults.map((option) => {
    	const isSelected = optionsSelected.includes(option);
      
      return {
      	name: option,
        value: option,
        isSelected
      }
    });
  }),
  
  actions: {
  	onChange() {
    	console.log(arguments);
    }
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

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

{{my-component}}

templates.components.my-component.hbs

{{yield}}

<select multiple onchange={{action "onChange"}}>
	{{#each selectOptions as |option|}}
  	<option selected={{option.isSelected}} value={{option.value}}>{{option.name}}</option>
  {{/each}}
</select>

twiddle.json

{
  "version": "0.13.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}