JQuery mCustomScrollbar autoScrollOnFocus

Solved

I'm using focus() function and mCustomScrollbar function scrollTo

$("#recaptcha_response_field").focus(function() {
  $(".scroller-back").mCustomScrollbar("scrollTo",this);
});

Code on Jsffidle

When the cursor has focus on recaptcha text field, the scroll will scrolling to on a line with recaptcha text field (scroll to self). But it's doesn't work when we use the tab key. I have tried with alert

$('#recaptcha_response_field').focus(function() {
  alert('Handler for .focus() called.');
});

Updated

I'm using scrollTo with target id's submit button.

var a=Recaptcha.$("recaptcha_response_field");

$(a).focus(function() {
  $(".scroller-back").mCustomScrollbar("scrollTo","#submit_button");
});

Code on Jsffidle