function trim(s) {
  // trim leading and trailing "whitespace"
  var whitespace = " \t\n\r";
  var i = 0;
  while ((i < s.length) && (whitespace.indexOf(s.charAt(i)) != -1)) i++;
  var j = s.length;
  while ((j > i) && (whitespace.indexOf(s.charAt(j-1)) != -1)) j--;
  return s.substr(i,j - i);
}

function isEmailValid(emailStr) {
    var emailPat=/^(.+)@(.+)$/;
    var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]";
    var validChars="\[^\\s" + specialChars + "\]";
    var quotedUser="(\"[^\"]*\")";
    var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
    var atom=validChars + '+';
    var word="(" + atom + "|" + quotedUser + ")";
    var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
    var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");

    var matchArray=emailStr.match(emailPat);
    if (matchArray==null) return false;

    var user=matchArray[1]
    var domain=matchArray[2]
    if (user.match(userPat)==null) return false;

    var IPArray=domain.match(ipDomainPat)
    if (IPArray!=null) {
        for (var i=1;i<=4;i++) {
            if (IPArray[i]>255) return false;
        }
        return true;
    }

    var domainArray=domain.match(domainPat)
    if (domainArray==null) return false;

    var atomPat=new RegExp(atom,"g");
    var domArr=domain.match(atomPat);
    var len=domArr.length;
    if (domArr[domArr.length-1].length<2 ||
        domArr[domArr.length-1].length>4) return false;

    if (len<2) return false;
    return true;
}