in-element-modal

components.my-component\.js

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

function openModal(element) {
  const modal = document.createElement('div');
  modal.className = 'modal';
  modal.appendChild(element);
  document.body.appendChild(modal);
}

export default class extends Component {
	@tracked modal = null;
  @tracked value = null;

  @action
  open() {
    this.modal = document.createElement('div');
    openModal(this.modal);
  }

  @action
  change() {
    this.value = "Content inside changing...";
  }
}

controllers.application\.js

import Controller from '@ember/controller';

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

styles.app\.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.modal {
  position: fixed;
  background: #ccc;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
}

templates.application\.hbs

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

templates.components.my-component\.hbs

<button {{on "click" this.open}}>Open Modal</button>

{{#if this.modal}}
	{{#-in-element this.modal}}
  	This is my modal!
    <button {{on "click" this.change}}>Change</button>
    {{value}}
  {{/-in-element}}
{{/if}}

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",
    "ember-data": "3.13.2"
  }
}