JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<p><input type="text" name="fname" value="abc"/></p>
<p><input type="submit" value="Submit"/></p>
</form>

JavaScript

document.querySelector("input[type=submit]").onclick = function(){
    var node = document.querySelector("input[name=fname]");
    node.setAttribute("value", node.value);
    return false;
}