如何实现在下拉菜单里输入文字？<script>functionpp(){se.options[2]=newOption(ok=(se.options[2])?se.options[2].innerText+String.fromCharCode(event.keyCode):String.fromCharCode(event.keyCode),"client")se.selectedIndex=2;}functionedit(){if(se.options[2]){if(event.keyCode==8){varstr=se.options[2].innerText;varlen=...