JSFiddle - React, Tailwind, and code Playground

HTML

<select id="update-select" multiple="multiple">
  <option value="3">Test1 </option>
  <option value="4">Test2 </option>
  <option value="5">Test3 </option>
  <option value="6">Test4</option>
  <option value="15">Test5</option>
</select>

<button id="test">Test</button>

JavaScript

$(function(){
    $("#test").on("click",function(){
        $("#update-select option:selected").each(function(i,elem){
           alert($(elem).val());
        });
    });
});