新手,请高手指教!!!
我自己写了一个简单的   JAVASCRIPT脚本验证,但是不知道为什么就是错误!!给指点并给出相关的资料!!谢谢   
  <script   language= "javascript ">  
  <!-- 
 function   checkspace(checkstr) 
 { 
 	var   str= ' '; 
 	for   (i=0;i <checkstr.length();i++) 
 	{ 
 		str=str+ '    '; 
 	} 
 	return   (str==checkstr); 
 } 
 function   ad_check() 
 { 
 	if(checkspace(document.adminform.admin.value)) 
 	{ 
 		document.adminform.admin.focus(); 
 		alert( "管理员不能为空! "); 
 		return   false; 
 	} 
 	if(checkspace(document.adminform.pasword.value)) 
 	{ 
 		document.adminform.pasword.focus(); 
 		alert( "密码不能为空 "); 
 		return   false; 
 	} 
 	document.adminform.submit(); 
 } 
 -->  
  </script>  
  <html>  
  <head>  
  <meta   http-equiv= "Content-Type "   content= "text/html;   charset=gb2312 "   />  
  <title> 管理员登录 </title>  
  <style>  
 table{background-color:#999933;margin-left:auto;margin-right:auto;margin-top:} 
 .adminhead{font-size:10px;font-color:#ccddff;font-family: "楷体_GB2312 ";align= "center "} 
  </style>  
  </head>    
  <body>  
  <form   action= "checkadmin.asp "   method= "post "   name= "adminform ">  
  <table   align= "center ">  
  <tr>  
  <td>  <div   style= "adminhead "> 后台登录 </div>  </td>  
  </tr>  
  <tr>  
 	 <table   align= "center ">  
 	 <tr>   </tr>  
 	 <tr>  
 	 <td>  <div   style= "adminhead "> 管理员: <input   type= "text "   name= "admin "   id= "admin "   size= "12 ">  </div>  </td>  
 	 </tr>  
 	 <tr>  
 	 <td>  <div   style= "adminhead "> 密 码: <input   type= "password "   id   = "pasword "   name= "pasword "   size= "12 ">  </div>  </td>  
 	 </tr>  
 	 <tr>  
 	 <td   colspan= "2 "   align= "center ">  <input   type= "button "      onClick= "return   ad_check() "   name= "sb "   value= "登录 ">   
 		 <input   type= "reset "   name= "rs "   value= "重置 ">  </td>  
 	 </tr>  
 	 </table>  
  </tr>  
  </table>  
  </form>  
  </body>  
  </html>
------解决方案--------------------checkstr.length() ——〉checkstr.length