https://stackoverflow.com/questions/54570864/search-by-start-with-not-containing-letter/54571012#54571012

https://stackoverflow.com/a/54571012/2678218

by apappas1129

HTML

<div class="select-options ps-container below ps-active-y">

  <input id="clientSearch" type="text">

<span>Bitcoin</span><span>Cat</span><span>Whiskey</span><span>Table</span>

CSS

span {
  display: block;
}

JavaScript

// OVERWRITES old selecor
jQuery.expr[':'].contains = function(a, i, m) {
  return jQuery(a).text().toUpperCase()
      .indexOf(m[3].toUpperCase()) >= 0;
};
 
 function searchClients() {
   var clientSearch = document.getElementById("clientSearch");
   var s = clientSearch.value;
   $("span").show();
   $("span").filter(function () {
    return !(new RegExp('^'+(s).toUpperCase()))
       .test((this.textContent || this.innerText || '').toUpperCase());
   }).hide();
 }

$("#clientSearch").keyup(function() {
  searchClients();
});