JSFiddle - React, Tailwind, and code Playground

HTML

<select id="diagnose_sicherheit" name="diagnose[sicherheit]" class="hidden-field" data-id="1377670814577-LN7za"><option value="V">Verdacht auf</option>
<option value="Z">Zustand nach</option>
<option value="A">Ausschluss</option>
<option value="G">Gesicherte Diagnose</option></select>
<input type="text" id="sicherheit"></input>

JavaScript

$(function(){
$("select[name^='diagnose']").change(function() {
   alert($(this).val());
$("#sicherheit").val($(this).val())
$( "#Scomit" ).click();
});
});