Just a note, this may not always work.
var acf_field = acf.getField('field_56e1cf2e7ad26');
acf_field.on("change ready", function(e){
The reason being that it will not work on fields that are dynamically added after the page is loaded. In one of the sites I’m working on I needed to do something like this
$(document).on('change', '[data-key="field_5b6c628cb8088"] .acf-input input', function(e) {
// ...
});