Computed

components.odds\.js

import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
import { action } from "@ember/object";

export default class extends Component {
  @tracked array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

  get odds() {
    console.log("evens called");
    return this.array.filter((n) => n % 2 === 1);
  }

  @action
  updateOdds() {
    this.array = [...this.array, 12, 14, 16, 18, 20];
  }

	primes() {
    
}

controllers.application\.js

import Controller from '@ember/controller';

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

templates.application\.hbs

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

templates.components.odds\.hbs

<div>Length: {{this.odds.length}}</div>
<div>First: {{this.odds.firstObject}}</div>

{{#each this.odds as |i|}}
  <div>{{i}}</div>
{{/each}}

<button type="button" {{on "click" this.updateOdds}}>
  Click Me
</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"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}