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>
