New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  hideButton: true
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  foo: [1, 2, 3, 4, 5, 6, 8, 9, 10]
});

templates.application.hbs

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

{{#each foo as |foo|}}
  <MyComponent />
{{/each}}

templates.components.my-component.hbs

<div
  onmouseenter={{action (mut this.hideButton) false}}
  onmouseleave={{action (mut this.hideButton) true}}
>
  wat
  

  	<button style="{{if this.hideButton "visibility: hidden;"}}">some button</button>
</div>

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"
  }
}