JS收藏，正则表达式

var usernamePatrn = /^([a-zA-Z0-9]|[_]){6,20}$/;if(!usernamePatrn.test(form.username.value)){alert("用户名输入按照规则");          return false; }

//去掉空格function  ltrim(s){   for(var i=0;i<s.length;i++)        if(s.charAt(i)!=' ')         return s.substring(i,s.length);     return "";}

<input type=button name="checkall" value="全选" onClick="this.value=check(this.form.checkbox)">var checkflag = "false";function check(field) {if (checkflag == "false") {for (i = 0; i < field.length; i++) {field[i].checked = true;}checkflag = "true";return "取消"; }else {for (i = 0; i < field.length; i++) {field[i].checked = false; }checkflag = "false";return "全选"; }}

<input type=submit name="del" value="删除" onClick="return checkDel();">//选择删除function checkDel(){var  check_id=document.getElementsByName("checkbox");var  id="";  for(i=0;i<check_id.length;i++){     if(check_id[i].checked){   id+=check_id[i].value+"##";     }  }if (id=="") {   alert ("请至少选择1个");   return false;}document.getElementById("userid").value=id;}