JS清除dropdownlist绑定的项，并添加新项

<script type="text/javascript">
/*删除项*/
document.getElementById('KeyList').options.length = 0;
/*添加项*/
document.getElementById("KeyList").options.add(new Option( "English Title", "en_title"));
document.getElementById("KeyList").options.add(new Option( "English Keywords", "en_key_word"));
document.getElementById("KeyList").options.add(new Option( "Abstract", "en_abstract"));
document.getElementById("KeyList").options.add(new Option( "Fund Project", "fund_project"));
document.getElementById("KeyList").options.add(new Option( "Institution(in English)", "en_institution"));
document.getElementById("KeyList").options.add(new Option( "DOI", "doi"));
document.getElementById("KeyList").options.add(new Option( "Author", "pin_yin_name"));
</script>