JSFiddle - React, Tailwind, and code Playground

HTML

<select id="select">
 <option value="defaultValue">Default</option>
 <option value="Option1">Option1</option>
 <option value="Option2">Option2</option>    
</select>
<input type="button" value="CHANGE" onclick="selectFunction()" />

JavaScript

var selectFunction = function() {
    document.getElementById("select").value = "defaultValue";
};