<test>
  <p>
    Lorem ipsum dolor sit amet.
  </p>
</test>
test {
  display: block;
}
registerCustomElement('test');

[].forEach.call(document.getElementsByTagName('test'), function(node) {
  node.addEventListener('click', function() {
    alert('!');
  });
});

function registerCustomElement(elements) {
  if (Array.isArray(elements)) {
    for (var i = 0; i < elements.length; i++ ) {
      document.createElement(elements[i]);
    }
  } else {
    document.createElement(elements);
  }
}

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External JavaScript

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