Validating that a signature box has been filled

Question

I'm trying to make the signature mandatory. I've looked through a lot of the posts and i can't seem to get any result. Javascript is not my strongest language, far from it.

I know the current code is probably far from what I need, I've tried about 5-10 different ways from doing it. I'm probably missing something completely stupid.

function CheckSignature() {
  var $sigdiv = $("Signature");
  var okay = $sigdiv.jSignature('getData', 'base30').length > 0 ? TRUE : FALSE;
  return okay;
}

Here's where my signature box is in my code

<div id = "SignatureRow" style="display:none;">
  <p class="SigPay">Signez ici: <img src="imagelinkhiddenforprivacy" class='VMid req' /></p>
  <div class = "Center">
    <img class = "SignX" src ="imagelinkhiddenforprivay"/>
    <div id ="Signature"></div>
    <input type="button" id = "ClearButton" value="Recommencer Signature" />
    <input name="base64customersig" type="hidden" class="uniquesignatureclass" />
  </div>