// Validation form fields

 //Check if the field is empty 
  function isEmptyField(str)
  {
     return ((str == null) || (str == "") || (str.length == 0));
  }
//Check if the e-mail is valid using a regular expression
  function isValidEmail(str)
  {  
    var email=/^.+@.+\..{2,3}$/;
    return (email.test(str));
  }
  
  //verify that user check at least one checkbox
function checkbox_checker()
{
   var checkbox_choices = 0;
   if (document.enrollment.Advertisement_Newspaper.checked)  { checkbox_choices +=  1; };
   if (document.enrollment.Website.checked)  { checkbox_choices +=  1; };
   if (document.enrollment.Search_Engine.checked)  { checkbox_choices +=  1; };
   if (document.enrollment.Yellow_Pages.checked)  { checkbox_choices +=  1; };
   if (document.enrollment.Family_Friend.checked)  { checkbox_choices +=  1; };
   if (document.enrollment.Linked_From_Another_Website.checked)  { checkbox_choices +=  1; };
   if (document.enrollment.Neighborhood_School.checked)  { checkbox_choices +=  1; };
   if (document.enrollment.Others.checked)  { checkbox_choices +=  1; };

   return checkbox_choices;
}


function doValidate()
{
  var userLastName    = document.getElementById("LastName");    
  var userFirstName   = document.getElementById("FirstName");    
  var userPhone       = document.getElementById("Phone");    
  var userEmail       = document.getElementById("Email");
  var userContactedBy = document.getElementById("ContactedBy");
 
     	
//last name: required 
  if (isEmptyField(userLastName.value)) 
  {
      alert("Please, enter your Last Name");
      userLastName.select();
      userLastName.focus();
      return false;
  }


//first name: required 
  if (isEmptyField(userFirstName.value)) 
  {
      alert("Please enter your First Name");
      userFirstName.select();
      userFirstName.focus();
      return false;
  }

// Contact Information: phone or e-mail
   if ( (isEmptyField(userPhone.value)) && (isEmptyField(userEmail.value)) )
  {
      alert("Please enter your Phone Number or/and E-mail address");
      userPhone.select();
      userPhone.focus();
      return false;
  }

//User e-Mail address: valid format
  if ( (isEmptyField(userEmail.value) == false) && (isValidEmail(userEmail.value) == false) )
  {
     alert("Please enter a valid Email Address");
     userEmail.select();
     userEmail.focus();
     return false;
  }
 
 
 //Contact Us by Phone 
   if ( (isEmptyField(userPhone.value)) && (userContactedBy.options[userContactedBy.selectedIndex].value == "Phone" ))
   {
	  alert("Please enter your Phone Number if you like to be contact by phone");
      userPhone.select();
      userPhone.focus();
      return false;	    
   }
   
    //Contact Us by E-mail 
   if ( (isEmptyField(userEmail.value)) && (userContactedBy.options[userContactedBy.selectedIndex].value == "E-mail" ))
   {
	  alert("Please enter your Email address if you like to be contact by e-mail");
      userEmail.select();
      userEmail.focus();
      return false;	    
   }
  
       //Verify that at least 1 checkbox is selected
   userCheckKnowUs = checkbox_checker();   
   if (  userCheckKnowUs == 0 )
   {
	  alert("Please tell us How did you know about us?");
      document.enrollment.Advertisement_Newspaper.select();
      document.enrollment.Advertisement_Newspaper.focus();
      return false;	    
   }    
  
 			  
  return true;
 }