The article explains how to extend the Advanced Custom Fields (ACF) WordPress plugin by creating custom field controls tailored to specific needs. It guides developers through building a custom “Country Selector” field, covering setup, defining field settings, rendering the field, adding scripts, and modifying saved values, highlighting ACF’s flexibility and support for enhancing user-friendly interfaces with custom JavaScript and styling.
http://www.smashingmagazine.com/2015/09/extending-advanced-custom-fields-with-your-own-controls