【www.gdgbn.com--php函数】

常用邮箱地址 ip地址 英文用户名验证函数

*/
// function to check e-mail address like string
 function isemail (s)
 {
  // there must be >= 1 character before @, so we
  // start looking at character position 1
  // (i.e. second character)
  var i = 1;
  var slength = s.length;

  if ( slength <= 1 ) return false ;

  // look for @
  while ((i < slength) && (s.charat(i) != "@"))
  { i++
  }

  if ((i >= slength) || (s.charat(i) != "@")) return false;
  else i += 2;

  // look for .
  while ((i < slength) && (s.charat(i) != "."))
  { i++
  }

  // there must be at least one character after the .
  if ((i >= slength - 1) || (s.charat(i) != ".")) return false;
  else return true;
 }

 // 验证ip地址主要用到正则([0-9]{1,3})[.]{1,}([0-9]{1,3})[.]{1,}([0-9]{1,3})[.]{1,}([0-9]{1,3})来处理了，因为ip是1.1.1.1这种规则哦，所以我们只要是符合规则就行了。function to check ip address like string
 function isipaddress ( stripaddress )
 {
  regexp = new regexp ( "([0-9]{1,3})[.]{1,}([0-9]{1,3})[.]{1,}([0-9]{1,3})[.]{1,}([0-9]{1,3})" ) ;
  aparts = regexp.exec ( stripaddress ) ;
  if ( aparts == null )
  {
   return false ;
  }

  if ( aparts.length != 5 )
  {
   return false ;
  }

  for ( nloopcnt = 1 ; nloopcnt < 5 ; nloopcnt ++ )
  {
   if ( aparts [ nloopcnt ] < 0 || aparts [ nloopcnt ] > 255 )
   {
    return false ;
   }
  }

  return true ;
 }

 //用户名只要是我们先定义一abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789-._@再遍历判断如果是不存在就不是合法的。
 function fn_checkloginname ( strlogin )
 {
  strlogin = trimstring( strlogin ) ;

  var checkok = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789-._@";
  var checkstr = strlogin ;
  var allvalid = true;
  for (i = 0;  i < checkstr.length;  i++)
  {
   ch = checkstr.charat(i);
   for (j = 0;  j < checkok.length;  j++)
     if (ch == checkok.charat(j))
    break;
   if (j == checkok.length)
   {
     allvalid = false;
     break;
   }
  }
  if ( ! allvalid )
  {
   return (false);
  }

  if ( checkstr.charat(0) == "-" || checkstr.charat(0) == "." || checkstr.charat(0) == "_" )
  {
   return (false);
  }

  return (true);
 }

本文来源：http://www.gdgbn.com/jiaocheng/28794/