// JavaScript Document
function checkFields(form) {

    if ( !checkEmailAddress(form.email.value) ) {
        form.email.value = "";
        alert("Please enter a valid email address.");
        form.email.focus();
        return false;
    }
}

function isBlank(s) {
    for ( var i=0;i<s.length;i++ ) {
        var c = s.charAt(i);
        if( (c != ' ') && (c != '\n') && (c != '\t') )
        return false;
    }
    return true;
}

// check email address characters
 function checkEmailAddress( 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>3) {
       return false
    }

    // Make sure there's a host name preceding the domain.
    if (len<2) {
       return false
    }
    return true;
  }