Attrs in init

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  init() {
    this._super(...arguments);
   	this._passedOnInit = this.passedValue;
    console.log(this.passedValue);
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Attrs in init</h1>
<br>
<br>
{{my-component passedValue=passedValue}}
<br>
<br>

templates.components.my-component.hbs

{{_passedOnInit}}

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"
  }
}