关于JS 联动，下拉框选项前后选择个数不同
或者直接看后面的问题 我向贴上我的代码，各位可运行一下。
2、在选这个
3、最后选择呢 学号，下拉框多呢几个。 多余的下拉选项是怎么产生的，求解决之道。
? js联动 js联动下拉框选项不一致
[解决办法]
<html>
<head>
<title>This is a test!</title>
</head>
<body>
<form name="frm">
<select name="s1" onChange="redirec(document.frm.s1.options.selectedIndex)">
<option value="id" selected>学号</option>
<option value="name">姓名</option>
<option value="age">年龄</option>
</select>
<select name="s2">
</select>
<input type="submit" value="查询"/>
</form>
<script language="javascript">
//获取一级菜单长度
var select1_len = document.frm.s1.options.length;
var select2 = new Array(select1_len);
//把一级菜单都设为数组
for(i=0; i<select1_len; i++)
{
select2[i] = new Array();
}
//定义基本选项
select2[0][0] = new Option("包含", "contain");
select2[0][1] = new Option("等于", "equal");
select2[1][0] = new Option("包含", "contain");
select2[1][1] = new Option("等于", "equal");
select2[2][0] = new Option(">", ">");
select2[2][1] = new Option("=", "=");
select2[2][2] = new Option("<", "<");
select2[2][3] = new Option("<=", "<=");
select2[2][4] = new Option(">=", ">=");
//联动函数
function redirec(x)
{
var temp = document.frm.s2;
temp.length=0;
for (i=0;i<select2[x].length;i++)
{
temp.options[i]=new Option(select2[x][i].text,select2[x][i].value);
}
alert("x："+x+" select2["+x+"].length："+select2[x].length);
temp.options[0].selected=true;
}
</script>
</body>
</html>
[解决办法]
<form name="frm">
<select name="s1" onChange="redirec(this.options.selectedIndex)">
<option value="id" selected>学号</option>
<option value="age">年龄</option>
<option value="name">姓名</option>
</select>
<select name="s2" id="s2"></select>
<input type="submit" value="查询"/>
</form>
<script language="javascript">
var arr = [
{"contain":"包含","equal":"等于"},
{">":">","=":"=","<":"<","<=":"<=",">=":">="}
];
function redirec(x){
x = x==1?1:0;
var s2 = document.getElementById("s2");//规范点
s2.options.length = 0;//清空下拉菜单
var obj = arr[x];
for(var k in obj){
s2.options.add(new Option(obj[k],k));
//新增下拉菜单，默认已经选中第一项
}
}
redirec(0);
</script>