【select】
<!DOCTYPE html>
<html>
<body>
<select id="ddl">
<option>A</option>
<option>B</option>
</select>
<script type='text/javascript'>
var originalOptions = document.getElementById('ddl').cloneNode(true).options;
console.log(originalOptions[0].innerText);
var selector = document.getElementById('ddl');
selector.options.length = 0;
console.log(originalOptions[0].innerText);
</script>
</body>
</html>
