JavaScript/ Php no response after email submit button

Question

Please could you help me I have the below javascript code everything works fine email validating works fine but when a visitor types in there email address and click sign up button the confirmation message 'You will be notified with our latest events!' doesn't show up.

  $(document).ready(function(){
 //Bind JavaScript event on SignUp Button
    $('#submitbtn').click(function(){
        signUp($('#email').val());
    }); 

var signUp = function(inputEmail)
{
    var isValid = true;
    var emailReg = /^([\w-\.]+@([\w-]+\.)+[\w-]{2,4})?$/;
    if(!emailReg.test(inputEmail)){
        isValid = false;
        alert('Your email is not in valid format');
    }
    if(isValid){
        var params = {
            'action'    : 'SignUp',
            'email'     : inputEmail
        };
        $.ajax({
            type: "POST",
            url: "scripts/mail.php",
            data: params,
            success: function(response){
                if(response){
                    var responseObj = jQuery.parseJSON(response);
                    if(responseObj.ResponseData)
                    {
                        $('#submitbtn').val('');
                        showMessage('You will be notified with our latest events!');

                    }
                }
            }
        });
    }
};

  var mousedownHappened = false;

  $("#submitbtn").mousedown(function() {
    mousedownHappened = true;
  });

  $("#email").focus(function(){
    $(this).animate({
      opacity: 1.0,
      width: '250px'
    }, 300, function(){
      // callback method empty
    });

    // display submit button
    $("#submitbtn").fadeIn(300);
  });


  $("#email").blur(function(){
    if(mousedownHappened) {
      // reset mousedown and cancel fading effect
      mousedownHappened = false;

    } else {
      $("#email").animate({
        opacity: 0.75,
        width: '250px'
      }, 500, function(){
        // callback method empty
      });

      // hide submit button
      $("#submitbtn").fadeOut(400);
    }
  });
});

Answer 1

As @Mike said you should add a failure handler to know if there was an error:

$.ajax({
        type: "POST",
        url: "scripts/mail.php",
        data: params,
        success: function(response){
            if(response){
                var responseObj = jQuery.parseJSON(response);
                if(responseObj.ResponseData)
                {
                    $('#submitbtn').val('');
                    showMessage('You will be notified with our latest events!');

                }
            }
        },

        error: function(response){ 
          showMessage('Sorry, there was an error saving you email. :(');
        }

    });

Edit: you have to add a ',' after close success function.

Answer 2

You have only an on-success handler. You need an error handler here. It looks like your AJAX call is actually going through, but coming back as an error and the $.ajax call has no way of reporting it. Read down to 'error' here to see what the error handler should look like. You should also set a break point at the start of your success and error handlers to make sure that at least one of them is called.