Riot

var tags = `
<pusher>
  <h3>{ message }</h3>
  <ul>
    <li each={ techs }>{ name }</li>
  </ul>

  <script>
    this.message = 'Hello, Riot!'
    this.techs = [
      { name: 'HTML' },
      { name: 'JavaScript' },
      { name: 'CSS' }
    ]
  </script>

  <style scoped>
    :scope { font-size: 2rem }
    h3 { color: #444 }
    ul { color: #999 }
  </style>
</pusher>
`;

if (!window.jQuery) {
  document.head.appendChild(
    Object.assign(document.createElement('script'), { src: 'https://code.jquery.com/jquery-2.2.3.js', onload: setup }),
  );
} else {
  setup();
}

function setup() {
  $.getScript('https://cdn.jsdelivr.net/riot/2.3/riot+compiler.min.js')
    .done(() => $('pusher, script[type="riot/tag"]').remove())
    .done(() => $('body').append($('<script type="riot/tag"></script>').text(tags)).append($(`<pusher></pusher>`)))
    .done(() => riot.mount('pusher'));
}

<!-- mount point -->
<my-tag></my-tag>

<!-- inlined tag definition -->
<script type="riot/tag">
  <my-tag>
    <h3>Tag layout</h3>
    <inner-tag />
  </my-tag>
</script>

<!-- <inner-tag/> is specified on external file -->
<script src="path/to/javascript/with-tags.js" type="riot/tag"></script>

<!-- include riot.js and the compiler -->
<script src="https://cdn.jsdelivr.net/riot/2.6/riot+compiler.min.js"></script>

<!-- mount normally -->
<script>
  riot.compile(my_tag.innerHTML);
  riot.mount('*');
</script>