how to call a jquery function code example

Example 1: how to call function in jquery

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

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

Example 2: how to create jquery function

(function( $ ){
   $.fn.myfunction = function() {
      alert('hello world');
      return this;
   }; 
})( jQuery );

$('#my_div').myfunction();