JSFiddle - React, Tailwind, and code Playground

HTML

<p>Teksti tulee <span id="sisalto">tähän</span></p>

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

<script src="javascript/code.js"></script>

JavaScript

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