JSFiddle - React, Tailwind, and code Playground
HTML
<select id="test">
<option value="1">1</option>
<option value="2">2</option>
</select>
<input type="button" id="b" value="Button"/>
JavaScript
$('#b').click(function(){
var s = document.getElementById('test');
var o = s.options[s.selectedIndex];
o.value=3;
console.log(o);
});