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<html>
<script type="text/javascript">
var selectedValue = '<%= request.getAttribute("line")%>'
function changeSelected(){
jsSelectItemByValue(document.getElementById("mySelect"),selectedValue)
}
function jsSelectItemByValue(objSelect,objItemText) {
for(var i=0i<objSelect.options.lengthi++) {
if(objSelect.options[i].value == objItemText) {
objSelect.options[i].selected = true
break
}
}
}
</script>
<body onload="changeSelected()">
<select id="mySelect" name="mySelect">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
</body>
</html>
<SELECT>标签用multiple属性来控制多选或单选，默认为单选，即没有multiple属性，所以设置单选则使用JS的removeAttribute函数移除multiple属性即可，代码如下所示：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html>
<head>
<title>Select 单选</title>
</head>
<body>
<select name="s2" size="6" style="width:100px" id="s2" multiple="multiple">
<option>选项1</option>
<option>选项2</option>
<option>选项3</option>
<option>选项4</option>
<option>选项5</option>
</select>
<script type="text/javascript">
var s2=document.getElementById("s2")
s2.removeAttribute("multiple")
</script>
</body>
</html>
效果如下：
可以使用javascript和jQuery两种实现方式1：使用javascript实现
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/htmlcharset=utf-8" />
<title>无标题文档</title>
</head>
<body>
<select name="jumpMenu" id="jumpMenu" onChange="jumpMenu('parent',this,0)">
<option id="1" value="跳转URL">111</option> // 111 是显示给用户的信息
<option id="2" value="跳转URL">222</option>
<option id="3" value="跳转URL">333</option>
<option id="4" value="跳转URL">444</option>
<option id="5" value="跳转URL">555</option>
</select>
<script type="text/javascript">
function display(optionID){
var all_options = document.getElementById("jumpMenu").options
for (i=0i<all_options.lengthi++){
if (all_options[i].id == optionID) // 根据option标签的ID来进行判断 测试的代码这里是两个等号
{
all_options[i].selected = true
}
}
}
display("4")
</script>
</body>
</html>
2：使用jQuery实现
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/htmlcharset=utf-8" />
<title>无标题文档</title>
</head>
<body>
<select name="jumpMenu" id="jumpMenu" >
<option value="1">111</option> // 111 是显示给用户的信息
<option value="2">222</option>
<option value="3">333</option>
<option value="4">444</option>
<option value="5">555</option>
</select>
<script type="text/javascript" src="js/jquery1.8.3.min.js"></script>
<script type="text/javascript">
$(function(){
// $("#jumpMenu").val(要选中的option的value值即可)
$("#jumpMenu").val(4)
})
</script>
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>New Document </title>
<meta name="Generator" content="EditPlus">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
</head>
<script type="text/javascript">
<!--
window.onload = function(){
document.getElementsByTagName('button')[0].onclick = function(){
// 不能有相同取值的下拉列表集合
var items = document.getElementsByTagName('select'),
len = items.length,
i = 0,
valMap = {},
sel,
val
// 遍历并保存各个下拉列表的值于valMap
for(i <leni++){
sel = items[i]
val = sel.options[sel.selectedIndex].value
// 没有相同的取值时保存该值，否则返回false
if(!valMap[val]){
valMap[val] = 1
}else{
alert('存在取值相同的下拉列表，取值为：' + val)
return false
}
}
// 校验通过，全部都不相同
return true
}
}
//-->
</script>
<body>
<button>Check</button>
<select>
<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>
<select>
<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>
<select>
<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>
<select>
<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>
<select>
<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>
<select>
<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>
<select>
<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>
</body>
</html>
