验证电子邮件的一个javaScript

function IsEmail (str)
 {
  if (str.length > 100)
  {
   return false;
  }
 
  var regu = "^(([0-9a-zA-Z_.]+)|([0-9a-zA-Z]+[_.0-9a-zA-Z-]*[0-9a-zA-Z_.]+))@([a-zA-Z0-9-]+[.])+([a-zA-Z]{2}|net|NET|com|COM|gov|GOV|mil|MIL|org|ORG|edu|EDU|int|INT)$"
  var re = new RegExp(regu);
  if (str.search(re) != -1)
   return true;
  else
   return false;
 }