Another good implementation method of secondary linkage_Form special effects

<table width="400" border="1" cellspacing="0" cellpadding="0" align="center" bordercolordark="#9cc384" bordercolorlight="#FFFFFF"> <tr bgcolor="#E6F0DD" align="center"> <td> <form method="post" action="a_list.asp" name="send" target="_blank"> <table width="62%" border="0" cellspacing="2" cellpadding="2"> <tr> <td width="44%" align="right">类别：</td> <td width="56%"> <table width="95%" border="0" cellspacing="0" cellpadding="0"> <tr> <td> <select name="class0" onchange="onselectchange()"> <option value="2">** 选择一级类别 **</option> <option value="0">A</option> <option value="1">B</option> </select> </td> </tr> <tr> <td> </td> </tr> <tr> <td> <select name="class1"> <option value="1">** 选择二级类别 **</option> </select> </td> </tr> </table> </td> </tr> </table> </form> </td> </tr> </table>
[Ctrl A select all Note: If you need to introduce external Js, you need to refresh to execute

]<script> <!-- function onselectchange(){ num=document.send.class0.options[document.send.class0.selectedIndex].value; switch(num){ case "0": document.send.class1.options.length=4; document.send.class1.options[00].text="A1"; document.send.class1.options[00].value=0; document.send.class1.options[01].text="A2"; document.send.class1.options[01].value=1; document.send.class1.options[02].text="A3"; document.send.class1.options[02].value=2; document.send.class1.options[03].text="A4"; document.send.class1.options[03].value=3; break; case "1": document.send.class1.options.length=6; document.send.class1.options[00].text="B1"; document.send.class1.options[00].value=0; document.send.class1.options[01].text="B2"; document.send.class1.options[01].value=1; document.send.class1.options[02].text="B3"; document.send.class1.options[02].value=2; document.send.class1.options[03].text="B4"; document.send.class1.options[03].value=3; document.send.class1.options[04].text="B5"; document.send.class1.options[04].value=4; document.send.class1.options[05].text="B6"; break; } } //--> </script>