JAVASCRIPT 点击显示 隐藏层

<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>点击显示/隐藏层</title> //code from www.gxlcms.com <style type="text/css"> a{text-decoration:none;} .tab{border:1px solid #e57243;border-top:0;margin:10px 0;text-align:left;width:200px;font-size:14px;} .th{border-top:1px solid #e57243;padding:5px;font-weight:700;clear:both;background:#f5e1d9;} .td{background:none;padding-left:37px;} </style> <script type="text/javascript"> function chg(id_num){ var oa = document.getElementById(id_num); var ob = document.getElementById("test_a"); if(oa.style.display == "block"){ oa.style.display = "none"; ob.innerHTML = "[+]"; }else{ oa.style.display = "block"; ob.innerHTML = "[-]"; } return false; } </script> </head> <body> 脚本之家，脚本编程基地。欢迎大家学习交流。 [-] <--点击 </body> </html>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]