jdanyow/index.html

## index.html
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>GistRun</title>
</head>
<body>
  <h1>Hello world!</h1>
  <form action="javascript:alert('submitted')">
    <fieldset>
      <legend>Choose at least one of these</legend>
      <label><input type="checkbox" id="firstinput"> apples</label>
      <label><input type="checkbox"> oranges</label>
      <label><input type="checkbox"> pineapple on pizza</label>
      <label><input type="checkbox"> flavor country</label>
    </fieldset>
    <button type="submit">Submit</button>
    <button type="button" onclick="javascript:firstinput.customValidity = ''">Clear custom validity</button>
  </form>
  <script>
    // expose a customValidity property for lit binding
    Object.defineProperty(HTMLInputElement.prototype, 'customValidity', {
      set(value) {
        this.setCustomValidity(value);
      }
    });
  </script>
  <script>
    firstinput.customValidity = 'You must check at least one of the checkboxes';
  </script>
</body>
</html>
	<!doctype html>
	<html lang="en">
	<head>
	<meta charset="utf-8">
	<title>GistRun</title>
	</head>
	<body>
	<h1>Hello world!</h1>
	<form action="javascript:alert('submitted')">
	<fieldset>
	<legend>Choose at least one of these</legend>
	<label><input type="checkbox" id="firstinput"> apples</label>
	<label><input type="checkbox"> oranges</label>
	<label><input type="checkbox"> pineapple on pizza</label>
	<label><input type="checkbox"> flavor country</label>
	</fieldset>
	<button type="submit">Submit</button>
	<button type="button" onclick="javascript:firstinput.customValidity = ''">Clear custom validity</button>
	</form>
	<script>
	// expose a customValidity property for lit binding
	Object.defineProperty(HTMLInputElement.prototype, 'customValidity', {
	set(value) {
	this.setCustomValidity(value);
	}
	});
	</script>
	<script>
	firstinput.customValidity = 'You must check at least one of the checkboxes';
	</script>
	</body>
	</html>