这个是一个在文本框中输入，自动选择的，你参考一下！<script LANGUAGE="JavaScript">
function jin_e(){
var index=-1;
var kx;
var temp;
kx=document.form1.text1.value;
for(var i=0;i<document.form1.select1.options.length;i++)
{
if(document.form1.select1.options[i].text==kx)
index=i;
}
if(index>=0)document.form1.select1.options[index].selected=true;
}
</script>
<form name="form1">
<input type=text name=text1 style="width:100px;" value="" onPropertyChange="return jin_e();">
<select name="select1" style="margin-left:100px;width:118px;">
<option value=1 selected>abc
<option value=2>a
<option value=3>acde
<option value=4>achh
</select>
</form>
function jin_e(){
var index=-1;
var kx;
var temp;
kx=document.form1.text1.value;
for(var i=0;i<document.form1.select1.options.length;i++)
{
if(document.form1.select1.options[i].text==kx)
index=i;
}
if(index>=0)document.form1.select1.options[index].selected=true;
}
</script>
<form name="form1">
<input type=text name=text1 style="width:100px;" value="" onPropertyChange="return jin_e();">
<select name="select1" style="margin-left:100px;width:118px;">
<option value=1 selected>abc
<option value=2>a
<option value=3>acde
<option value=4>achh
</select>
</form>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>JK:支持民族工业,尽量少买X货</title>
<style>
.afterPreviousFont
{
position:absolute;
width:20;
overflow:hidden;
direction:rtl;
left:expression(this.previousSibling.offsetLeft+this.previousSibling.offsetWidth-1);
}
</style></head><body>
可输入下拉框，用来凑热闹，没什么实际用途<br>
请输入：<input style="width:100" onchange="this.nextSibling.all[0].value=this.value;"><font class="afterPreviousFont" >
<select style="width:120" dir=ltr onchange="this.parentElement.previousSibling.value=this.value;"><option value="">
<option value="abcde">abcde</option>
<option value="this is jk glad to meet you">this is jk glad to meet you</option>
</select>
</font>
</body></html>
http://jkisjk.vip.sina.com/html/EditableSelect1.htm可输入下拉框(20041126)(相似高亮显示，不相似不移除)
http://jkisjk.vip.sina.com/html/EditableSelect2.htm