SO classNameBindings example

components.x-example.js

import Ember from 'ember';

export default Ember.Component.extend({
  classNames: ['component'],
  classNameBindings: [
   	'flag:emberClassA:emberClassB'
  ],
  
  flag: false,
  
  didRender() {
    Ember.run.scheduleOnce('afterRender', this, this.restoreJQueryClass);
  },
  
  restoreJQueryClass() {
    if (this._savedClassState) {
    	this.$().addClass('jQueryClass', this._savedClassValue);
    }
  },
  
  actions: {
   	toggleFlag () {
      this.toggleProperty('flag');
    },
    toggleClassFromOutside () {
      this.$().toggleClass('jQueryClass');
      this.set('_savedClassState', this.$().hasClass('jQueryClass'));
    }
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<style>
	.component {
  	min-height: 150px;
  }
</style>
<p>
  Button A toggles a class that changes the background color through the <code>classNameBindings</code> attribute
</p>
<p>
	Button B uses jQuery to toggle a class that adds a green border.
</p>
<p>
	If the class through jQuery is added and then the ember button is pressed, the jQuery class is lost.
</p>
{{x-example}}

templates.components.x-example.hbs

<style>
	.emberClassA {
  	background: red;
  }
  .emberClassB {
  	background: blue;
  }
  .jQueryClass {
  	border: 10px solid green;
  }
</style>
<button type="button" {{action "toggleFlag"}}>
	A) Toggle ember classNameBindings
</button>
<br />
<button type="button" {{action "toggleClassFromOutside"}}>
	B) Change class with jQuery
</button>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}