JSFiddle - React, Tailwind, and code Playground

HTML

<p>Select a new car from the list.</p>

<select id="Car" multiple="on" size="5" onchange="myFunction()">
  <option value="Audi">Audi
  <option value="BMW">BMW
  <option value="Mercedes">Mercedes
  <option value="Volvo">Volvo
</select>
<br>
The car is:
<p id="demo"></p>

JavaScript

function myFunction() {
    var sSelected = '';
    [].forEach.call(  document.querySelectorAll('#Car :checked')  , function(elm){
       	if(sSelected !== '') sSelected += ', ';
    	 sSelected += elm.value;
		})
    document.getElementById("demo").innerHTML = "You selected: " + sSelected;
}