Calling a user defined function in jQuery

If you want to call a normal function via a jQuery event, you can do it like this:

$(document).ready(function() {
  $('#btnSun').click(myFunction);
});

function myFunction() {
  alert('hi');
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button id="btnSun">Say hello!</button>