Property settling

components.my-component.js

import Ember from 'ember';
import { observer, computed } from '@ember/object';

export default Ember.Component.extend({
  obsCallCount: 0,
  
  prop1: computed('prop2', function () {
    return this.get('prop2') + '123';
  }),
  
  prop1Observer: observer('prop1', function () {
    this.incrementProperty('obsCallCount');
    const prop1 = this.get('prop1');
    this.set('prop2', prop1.substring(0, prop1.length - 4));
  }),
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
{{my-component}}
<br>
<br>

templates.components.my-component.hbs

CallCount: {{obsCallCount}}<br />

prop1: {{prop1}}<br />
prop2: {{prop2}}<br />
{{input value=prop2}}

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"
  }
}