//Declares random Math values for variables used in equation
var NumA=(Math.floor(Math.random()*11));
var NumB=(Math.floor(Math.random()*11));
var NumC=NumA+NumB;

//-------------

//This function trims whitespace
function trim(s)
{
  return s.replace(/^\s+|\s+$/, '');
} 


function checkform (form)
{
//Validates Name value
    var error = "";
  
    if (form.sendername.value.length == 0) {
	form.sendername.focus();
        form.sendername.style.background = 'Yellow'; 
        alert("You didn't enter your name.");
        return false;
    } else {
        form.sendername.style.background = 'White';
        //return true;
    }
       
//-------------

//Validates Sender Email Value
    var error="";
    var tfld = trim(form.senderEmail.value);        // value of field with whitespace trimmed off
    var emailFilter = /^[^@]+@[^@.]+\.[^@]*\w\w$/ ;
    var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/ ;
    
    if (form.senderEmail.value == "") {
	form.senderEmail.focus();
        form.senderEmail.style.background = 'Yellow';
        alert("You didn't enter a sender email address.");
        return false;
    } else if (!emailFilter.test(tfld)) {              //test email for illegal characters
	form.senderEmail.focus();
        form.senderEmail.style.background = 'Yellow';
        alert("Please enter a valid sender email address.");
        return false;
    } else if (form.senderEmail.value.match(illegalChars)) {
	form.senderEmail.focus();
        form.senderEmail.style.background = 'Yellow';
        alert("The sender email address contains illegal characters.");
        return false;
    } else {
        form.senderEmail.style.background = 'White';
		//return true; 
   }
    
//-------------

//Validates Receiver Email value

    var error="";
    var tfld = trim(form.receiverEmail.value);        // value of field with whitespace trimmed off
    var emailFilter = /^[^@]+@[^@.]+\.[^@]*\w\w$/ ;
    var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/ ;
    
    if (form.receiverEmail.value == "") {
	form.receiverEmail.focus();
        form.receiverEmail.style.background = 'Yellow';
        alert("You didn't enter a receiver email address.");
        return false;
    } else if (!emailFilter.test(tfld)) {              //test email for illegal characters
	form.receiverEmail.focus();
        form.receiverEmail.style.background = 'Yellow';
        alert("Please enter a valid receiver email address.");
        return false;
    } else if (form.senderEmail.value.match(illegalChars)) {
	form.receiverEmail.focus();
        form.receiverEmail.style.background = 'Yellow';
        alert("The receiver email address contains illegal characters.");
        return false;
    } else {
        form.receiverEmail.style.background = 'White';
		//return true; 
   }
   
//---------------

//Validates Math Value

  if (form.math.value != NumC) {
    form.math.focus();
    form.math.style.background = 'Yellow'; //changes form field background upon validation
    alert("Please enter the correct Math Validation sum.");
    return false ;
  }
  form.math.style.background = 'White';
  return true ;
}
// End of Javascript