JSFiddle - React, Tailwind, and code Playground

HTML

<script>
    function f1(){ alert('hello world'); };
</script>

<a onclick="f1()">test</a>
<div>testDiv</div>

JavaScript

debugger
var defaultFunction = $('a').attr('onclick');
defaultFunction = defaultFunction.substring(0, defaultFunction.indexOf('('));

$('div').on('click', function(){
    
   if(typeof window[defaultFunction] ==="function")
   {
   window[defaultFunction]();
   }
    alert('Hello universe!');
});