转:JavaScript中的三级联动

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<meta name="Copyright" content="爱JavaScript中文网 http://www.ijavascript.cn/" />
<meta name="description" content="三级联动，分享个人的JavaScript学习经历,做最好的JavaScript资料分享站点" />
<meta content="三级联动,爱JavaScript中文网" name="keywords" />
<title>三级联动演示 - 爱JavaScript中文网</title>

<SCRIPT LANGUAGE="JavaScript">
<!--

var t = new Array();

t["111"]="农业用品及食品";
t["111001"]="食品类";
t["111002"]="农业用品";
t["111001001"]="营养补给品";

var bit = 3;
var defaultVal = "122009036";

function setVal(objSel)
{
var v = objSel.options[objSel.selectedIndex].value;
var ov = document.getElementById('v');
if(v == "")
{
    if (ov != null)
    {
      v = ov.value;
      var d = objSel.getAttribute("d") != null ? objSel.getAttribute("d") : 0;
      v = v.substr(0, bit * (d - 1));
    }
}

if (ov != null)
ov.value = v;

}

function LoadData(objSelId, val, defaultVal)
{
var i = 0, d=0;
var c;
var objSel = document.getElementById(objSelId);
if (objSel == null)
return;

d = objSel.getAttribute("d") != null ? objSel.getAttribute("d") : 0;
if(objSel.getAttribute("c") != null)
{
c = objSel.getAttribute("c");
}

var len = d * bit;
objSel.options.length = 0;
objSel.options.add(new Option( "Please select", ""));

for (var k in t)
{
    if (k.length == len && k.substr(0, len-bit) == val.substr(0, len-bit))
    {
      objSel.options.add(new Option( t[k], k));
      if (k == defaultVal.substr(0, len))
        i = objSel.options.length - 1;
    }
}

if (i > 0)
{
objSel.selectedIndex = i;
}

setVal(objSel);

if (c != null)
LoadData(c, defaultVal, defaultVal);

if(c != null)
{
objSel.onchange = Function( "LoadData('"+c+"', this.options[this.selectedIndex].value, '');setVal(this);" );
}
else
{
objSel.onchange = Function( "setVal(this);" );
}
}

function Init()
{
LoadData("s1", "", defaultVal);
}

//-->
</SCRIPT>

</HEAD>