had same issue – your solution didn’t work for me, E’s solution did. So I just want you to know about it incase. I’m using ACF5Pro.
I put this in as last script before /body. Though I suppose it only has to be below the ACF scripts. I’m using acf_form() w/o the form component to load a repeater field, and navigating away after changes to that field were causing that popup to appear. But no now. 🙂
link for ref: http://support.advancedcustomfields.com/forums/topic/disable-acf_form-navigate-away-warning/#post-27915
<script>
(function($) {
$(document).ready(function() {
// disable the ACF js navigate away pop up
acf.unload.active = false;
});
})(jQuery);
</script>
</body>
