When I worked in a company project, we need a international telephone input plugin. There is a good jQuery plugin for it https://intl-tel-input.com/. But we find out that the plugin doesn't support searching or filtering. When the list of items become bigger, it's difficult to find the desired the item by scrolling.
I decided to add the filtering functions for the jQuery plugin. After forking the original jquery plugin repository, I added filtering by telephone coutnry code or filtering by country name.