How to get value of searchbox input field on bootstrap-select?

Here is my html code:

 <select id="myselect" class="selectpicker" data-live-search="true" placeholder="please type" data-live-Search-Placeholder="search">
   <option value="111">AAAAAAAAAAA</option>
   <option value="222">bbbbbbbbbbb</option>
   <option value="333">cccccccccc</option>
</select>

Here is my javascript code:

$(function(){
   var select1 = $('#myselect').selectpicker();
    //var mysearchkeyword = $('#myselect').selectpicker('search.initiated').val();
    //var mysearchkeyword = $('#myselect').selectpicker('search.input').val();
    var mysearchkeyword = $('#myselect').selectpicker('.bs-searchbox').val();

   select1.on('changed.bs.select', function (e) {
    alert(mysearchkeyword);
    
   });
})

Here is my fiddle: JSFiddle

I want to get the data of searchbox input in bootstrap-select. For example if I type “a” in searchbox I want it to get the “a” as alert message. I read this guide and tried a few ways but it didn’t work. Can you please help me?

Thanks in advance.