function isBlank(str){
  var blankCheck = /^ *$/;
  return blankCheck.test(str);
}

function validateField(obj){
  var reEmail = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;


  if(isBlank(obj.name.value)){
    alert('Name is a required field!');
	obj.name.focus();
	return false;
  }

  if(isBlank(obj.phone.value)){
    alert('Phone is a required field!');
	obj.phone.focus();
	return false;
  }

  if(isBlank(obj.zip.value)){
    alert('Zip is a required field!');
	obj.zip.focus();
	return false;
  }

  if(!isBlank(obj.email.value)){
  	if (!reEmail.test(obj.email.value)){
    	alert("Invalid email address!");
		obj.email.focus();
		return false;
 	 }
  }
  
  return true;
}