JSFiddle - React, Tailwind, and code Playground

HTML

<p id="teksti"></p>

<input type="text" name="nimi" id="tekstikentta" />
<input type="button" onclick="aseta()" value="Aseta"/>

JavaScript

function aseta() {
    var arvo = document.getElementById("tekstikentta").value
    document.getElementById("teksti").innerHTML = arvo
}