New Twiddle

components.expandable-list.js

import Ember from 'ember';

const { computed } = Ember;

export default Ember.Component.extend({
  isExpanded: false,
  maxCollapsed: 5,
  viewableContent: computed('maxCollapsed', 'content.[]', 'content.length', 'isExpanded', function() {
    const { content, isExpanded } = this.getProperties('content', 'isExpanded', 'maxCollapsed');
    
    if (isExpanded) {
      return content; 
    } else {
      return content.slice(0, this.get('maxCollapsed'));
    }
  }),
  
  actions: {
    toggle() {
      this.toggleProperty('isExpanded'); 
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  apps: Ember.computed(function() {
    const content = [];
    for (let x = 0; x < 10; x++) {
      content.push({
        id: x,
        name: `App ${x}`
      });
    }
    return content;
  })
});

templates.application.hbs

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

{{#expandable-list content=apps as |el|}}
  <ul>
	{{#each el.items as |app|}}
  	<li>{{app.name}}</li>
  {{/each}}
  </ul>
  
  <button {{action el.toggle}}>
  	{{#if el.isExpanded}}
	    Collapse
    {{else}}
    	View all ({{apps.length}}) apps.
    {{/if}}
  </button>
{{/expandable-list}}

{{#expandable-list content=apps as |el|}}
  <ul>
	{{#each el.items as |app|}}
  	<li>{{app.name}}</li>
  {{/each}}
  </ul>
  
  <button {{action el.toggle}}>
  	{{#if el.isExpanded}}
	    Collapse
    {{else}}
    	View all ({{apps.length}}) apps.
    {{/if}}
  </button>
{{/expandable-list}}

templates.components.expandable-list.hbs

{{yield (hash items=viewableContent toggle=(action 'toggle') isExpanded=isExpanded)}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}