JSFiddle - React, Tailwind, and code Playground

HTML

<button type="button" onclick="javascript:impostaRicerca()" id="ricerca">Popola casella di ricerca</button>
<iframe id="mioframe" src="http://www.bing.it" width="600" height="400"></iframe>

JavaScript

window.impostaRicerca = function() {
    document.getElementById("mioframe").contentDocument.getElementById("sb_form_q").value = "Ciao";
};