replacing array

controllers.application\.js

import Controller from '@ember/controller';
import { tracked } from '@glimmer/tracking';
import { action, computed } from '@ember/object';

class Item {
  @tracked name;
  
  constructor(name) {
    this.name = name; 
  }
}

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';

  @tracked
  arr = [new Item('foo'), new Item('bar')];

  @computed('arr.@each.name')
	get names() {
    return this.arr.map(({name}) => name.toUpperCase()).join(', '); 
  }

  @action
  replaceSecondName() {
    this.arr[1].name = 'lol';
  }

  @action
  replaceArr() {
     this.arr = [new Item('baz'), new Item('quux'), new Item('zomg')];
  }
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>

<p>
  names: {{this.names}}
</p>

<p>
  <button {{on 'click' this.replaceSecondName}}>
    Replace second name
  </button>
  
  <button {{on 'click' this.replaceArr}}>
    Replace whole array
  </button>
</p>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}