New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  html: `<div>
  <img src="https://via.placeholder.com/350x150" width="350" height="150" alt="Placeholder" />
</div>`,
});

controllers.application.js

import Ember from 'ember';

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

instance-initializers.mutation-observer.js

export default {
  name: 'mutation-observer',
  initialize(application) {
    new MutationObserver(mutations => {
      mutations.forEach(mutation => {
        if (mutation.target.tagName === 'img') {
          console.log('Image Found', mutation);
        }
      });
      if (!mutations.some(m => m.target.tagName === 'img')) {
        console.log('Image Not Found', mutations);
        return
      }
      
      console.log('some images found')
    }).observe(document.documentElement, {
      childList: true,
      subtree: true,
      attributes: true,
    });
  }
};

templates.application.hbs

{{my-component}}

templates.components.my-component.hbs

Stuff<br />
<div>
	{{log 'rendering' html}}
  {{{html}}}
</div>
Things <br />

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"
  }
}