JSFiddle - React, Tailwind, and code Playground

HTML

<select id="Nazione" name="Nazione">
    <option prefix='+93' value='AF' >Afghanistan </option>
    <option prefix='+355' value='AL' >Albania </option>
    <option prefix='+213' value='DZ' >Algeria </option>
    <option prefix='+376' value='AD' >Andorra .... etc</option>
</select>

JavaScript

$('#Nazione').change(function(){
       alert( $(this).find("option:selected").attr('prefix') );
       alert( $(this).attr('prefix') );
});