validating form field via ajax

validating form field via ajax

I'm using jQuery validate.  I'm trying to use ajax to see if an email address is already taken. My form is #new_user.

$('#new_user').validate({
    rules: {
      'user[email]': {
        required: {
          depends: check_email
        },
        email: true
      }
      ...

  function check_email()
  {
    var email_address = $("#user_email").val();
    $.post("/checkuser",{ email: email_address } ,function(data) {
        if (data != 'true') {
             return false;
        } else { //if username not avaiable
             return true;
        }
      });
  }

But this doesn't work.