function ValidateForm(){

var typed = document.ask_Phone.phoneNumber.value

   if (typed == "ledenlijst" || typed == "ledenlijsta" || typed == "ledenlijstd"){
     return true
   }

   if (today>=eventDate && typed.charAt(typed.length-1) != "@"){
      alert('Today is at or past the event date of ' + fulleventDate + '\nYou can no longer reserve for this event')
      return false;
   }

   if(IsEmpty(document.ask_Phone.phoneNumber)){ 
      alert('You have not entered a 10-digit phone number') 
      document.ask_Phone.phoneNumber.focus(); 
      return false; 
   } 
 
   PureNumbers=ExtractNumeric(typed)

   if (!Is_10_Digits(PureNumbers)){ 
      alert('Please enter a 10-digit phone number') 
      document.ask_Phone.phoneNumber.focus(); 
      return false; 
   } 

return true;
 
}

function IsEmpty(aTextField) {
   if ((aTextField.value.length==0) ||
   (aTextField.value==null)) {
      return true;
   }
   else { return false; }
}	

function ExtractNumeric(sText){
   var ValidChars = "0123456789";
   var Number="";
   var Char;
   for (i = 0; i < sText.length; i++){
      Char = sText.charAt(i); 
        if (ValidChars.indexOf(Char) != -1){ 
         Number = Number + Char;
        }       
      }
   return Number;   
   }

function Is_10_Digits(sText){
   if (sText.length==10){
     return true;
   }
   else {return false; }
}

with (document){

write ('<table border="2" bgcolor="yellow"><tr><td align=center>') 
write ('<b>HAC Reservation System</b><br>If you wish to attend this event, please reserve<br>by entering and submitting your<br>10-digit phone number below:')

write ('<form method="post" name="ask_Phone" action="search_HAC.php" onSubmit="return ValidateForm()" >')
write ('<input type = "text" name="phoneNumber">')
write ('<input type="submit" value="Submit">')
write ('</form>')
write ('</td></tr></table>')
write ('<script type="text/javascript">')
write ('document.ask_Phone.phoneNumber.focus();')
write ('</script>')
}