Anti-spam Measures in Javascript

First add Random Number generators

Put this in your header with your form validation functions so these variables are created every time the page loads:

  function getRandom_0to10(){
    var seed = Math.random();
    //Multiply to create number 0.0-9.99, then round to integer
    return seed = Math.ceil(seed * 10); 
  }
  var x = getRandom_0to10(); // this is "x"
  var y = getRandom_0to10(); // this is "y"
  var answer = x + y;        // this is what they add up to 
  

Then add the line to your Form

<p>Please add these two numbers:
  <script type="text/javascript">
    document.write(x + " + " + y +" = ");
  </script>
<input name="arithmetic" type="text" class="required add" 
   id="arithmetic" value=" " size="4" maxlength="2" />
</p>

Which displays as (with actual random numbers replacing the "x" and "y"):

Please add these two numbers: x + y =

Then add validation for this item

Add a parameter to your validation function (additions in red):

function validateForm(whichform,sumanswer){

and to the way you call it:

<form id="survey" name="survey"
onsubmit="return validateForm(this,answer)"
action="/cgi-bin/form-mail/~webclass/raneym3/forms/form.cfg" method="post"/>

Add this to your validation function after you've checked other parameters:

	 
//validate addition
if (element.className.indexOf("add") != -1){
  if(element.value != sumanswer){
    alert ("Check your answer on the addition problem.");
    return false;
  }
}
      

For a demo of this, go to my form on the NAS server