function isValidEmail(email, required) {

if (required==undefined) {   // if not specified, assume it's required

required=true;


}


if (email==null) {


        if (required) {


            return false;


        }


        return true;


    }


    if (email.length==0) {  


        if (required) {


            return false;


        }


        return true;


    }


    if (! allValidChars(email)) {  // check to make sure all characters are valid


        return false;


    }


    if (email.indexOf("@") < 1) { //  must contain @, and it must not be the first character


        return false;


    } else if (email.lastIndexOf(".") <= email.indexOf("@")) {  // last dot must be after the @


        return false;


    } else if (email.indexOf("@") == email.length) {  // @ must not be the last character


        return false;


    } else if (email.indexOf("..") >=0) { // two periods in a row is not valid


            return false;


    } else if (email.indexOf(".") == email.length) {  // . must not be the last character


            return false;


    }


    return true;


}


 

 

function allValidChars(email) {


  var parsed = true;


  var validchars = "abcdefghijklmnopqrstuvwxyz0123456789@.-_";


  for (var i=0; i < email.length; i++) {


    var letter = email.charAt(i).toLowerCase();


    if (validchars.indexOf(letter) != -1)


      continue;


    parsed = false;


    break;


  }


  return parsed;


}