JSFiddle - React, Tailwind, and code Playground

HTML

<select id="test" multiple="true">
    <option value="1">Test One</option>
    <option value="2">Test Two</option>
</select>

<button id="test1">Try &quot;outdated&quot;</button>
<button id="test2">Try &quot;nice HTML5 one-liner&quot;</button>
<button id="reset">Select none</button>

JavaScript

function outdated(id) {
  let elt = document.getElementById(id);

  if (elt.selectedIndex == -1)
    return null;

  return elt.options[elt.selectedIndex].text;
}

function nice_html5_one_liner(id) {
	return document.getElementById(id).selectedOptions[0].text;
}

function call_wrapped(fn, id) {
	try {
  	console.log(fn(id));
  } catch (e) {
  	alert(e);
  }
}

document.getElementById('test1').onclick = () => call_wrapped(outdated, 'test');
document.getElementById('test2').onclick = () => call_wrapped(nice_html5_one_liner, 'test');
document.getElementById('reset').onclick = () => document.getElementById('test').selectedIndex = -1;