James

controllers.application\.js

import Controller from '@ember/controller';
import { action } from "@ember/object";
import { tracked } from "@glimmer/tracking";
import { A } from '@ember/array';
import {
  TrackedArray,
} from 'tracked-built-ins';

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

  get arrayA() {
    return [1, 2, 3];
  }

  @action
  addToArrayA() {
    alert('added to array a');
    // this.arrayA.insertAt(1, 'aaaa');
    this.arrayA.push('bbb');
  }

  @tracked
	arrayB = new TrackedArray([1, 2, 3]);

	constructor() {
    super(...arguments);
    this.initColumns(); 
  }

	initColumns() {
    const b = this.arrayB;
    
    b.push('a');
  }

  @action
  addToArrayB() {
    alert('added to array b');

    // this.arrayB.push('bbb');
    this.arrayB.insertAt(1, 'aaaa');
    
	    // this.arrayB.clear();

    // this._arrayB = new TrackedArray([3, 4, 5]);
    
  }

  _arrayC = A([1, 2, 3]);

  get arrayC() {
    return this._arrayC;
  }
  @action
  addToArrayC() {
    alert('added to array C');
    // this.arrayC.insertAt(1, 'aaaa');
    this.arrayC.pushObject('bbb');
  }
}

templates.application\.hbs

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

<h1>Array A</h1>
{{this.arrayA}}

{{#each this.arrayA as |a|}}
	{{a}},
{{/each}}

<button {{on "click" this.addToArrayA}}>Add to arrayA</button>

<hr>

<h1>Array B</h1>
{{this.arrayB}}

{{#each this.arrayB as |b|}}
	{{b}},
{{/each}}

<button {{on "click" this.addToArrayB}}>Add to arrayB</button>

<hr>

<h1>Array C</h1>
{{this.arrayC}}

{{#each this.arrayC as |c|}}
	{{c}},
{{/each}}

<button {{on "click" this.addToArrayC}}>Add to arrayC</button>

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",
    "tracked-built-ins": "1.1.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0",
        "tracked-built-ins": "1.1.1"
  }
}