JSFiddle - React, Tailwind, and code Playground
by wisegorilla
HTML
<select class="select" id="province" onchange="filterCity();">
<option value="1">RM</option>
<option value="2">FI</option>
</select>
<select class="select" id="city" disabled>
<option data-province="RM" value="1">ROMA</option>
<option data-province="RM" value="2">ANGUILLARA SABAZIA</option>
<option data-province="FI" value="3">FIRENZE</option>
<option data-province="FI" value="4">PONTASSIEVE</option>
</select>
<span id="option-container" style="visibility: hidden; position:absolute;"></span>
JavaScript
function filterCity(){
var province = $("#province").find('option:selected').text(); // stores province
$("#option-container").children().appendTo("#city"); // moves <option> contained in #option-container back to their <select>
var toMove = $("#city").children("[data-province!='"+province+"']"); // selects city elements to move out
toMove.appendTo("#option-container"); // moves city elements in #option-container
$("#city").removeAttr("disabled"); // enables select
};