JSFiddle - React, Tailwind, and code Playground

HTML

<select id="testID" multiple="multiple">
   <option value="1">test Value1</option>
   <option value="2">test Value2</option>
   <option value="3">test Value3</option>
   <option value="4">test Value4</option>
   <option value="5">test Value5</option>
  <option value="6">test Value6</option>
</select>

<input type="button" value="Get dropdown selected Value" id ="select-values">
    <div id="selection"></div>

JavaScript

$("#select-values").click(function () {   
    var select = "";
    $("select option:selected").each(function(){
        select += ","+$(this).text();
    });
    if(select != ""){
        select = select.substr(1);
    }
    $("#selection").text(select);
});