didUpdateAttrs

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  
  init() {
  	this._super(...arguments);
    this.set('messages', []);
  },
  
  classNames: ['my-component' ],
  
  didReceiveAttrs() {
  	this.get('messages').pushObject('didReceiveAttrs was hit!');
  }
  
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  attr1: 'attr1',
  attr2: 'attr2',
  attr3: 'attr3',
  
  actions: {
  	updateAttributes (howMany) {
    	if (howMany === 1) {
      	this.set('attr1', Date.now());
      }
      if (howMany === 2) {
      	this.setProperties({
          attr1: Date.now(),
        	attr2: Date.now()
        });
      }
      if (howMany === 3) {
        this.setProperties({
          attr1: Date.now(),
        	attr2: Date.now(),
          attr3: Date.now()
        });
      }
    }
  }
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}
.my-component {
	border: solid 2px gray;
}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<button {{action 'updateAttributes' 1}}>update 1 attribute</button>
<button {{action 'updateAttributes' 2}}>update 2 attributes</button>
<button {{action 'updateAttributes' 3}}>update 3 attributes</button>
<br>
{{my-component attr1=attr1 attr2=attr2 attr3=attr3}}

templates.components.my-component.hbs

<ul>
	<li>attr1: {{attr1}}</li>
  <li>attr2: {{attr2}}</li>
  <li>attr3: {{attr3}}</li>
</ul>

<ul>
	{{#each messages as |item|}}
  	<li>{{item}}</li>
  {{/each}}
</ul>

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"
  }
}