<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
</HEAD>
<BODY>
<table>
<tr>
<td>
<select id="L" size=10>
</select>
</td>
<td>
<input type="button" value="<<" onclick="addLeft()"><br><input type="button" onclick="addRitht()" value=">>">
</td>
<td>
<select id="R" size=10>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
</td>
</tr>
<SCRIPT LANGUAGE="JavaScript">
<!--
function addLeft(){
var v = document.getElementById("R");
var index=v.selectedIndex; //序号，取当前选中选项的序号
if(index==-1){
alert("请选择要添加项！");
return;
}
var val = v.options[index].value;
var name = v.options[index].text;
if(check(val,"L")==1)
return;
var L = document.getElementById("L");
L.options.add(new Option(name,val));
}
function addRitht(){
var v = document.getElementById("L");
var index=v.selectedIndex; //序号，取当前选中选项的序号
if(index==-1){
alert("请选择要取消项！");
return;
}
v.options.remove(index);
}
function check(val,name){
var obj = document.getElementById(name);
var newVal = -1;
for(var i=0;i<obj.options.length;i++){
newVal = obj.options[i].value;
if(val==newVal){
alert("该项已存在！");
return 1;
}
}
return 0;
}
//-->
</SCRIPT>
</BODY>
</HTML>