Js if function exist then execute the code

if ($.fn.functioname) {
  //Your code here
}

//Example
if ($.fn.countdown) {
		$('#ic-countdown').countdown('2019/01/01', function(event) {
		    $(this).html(event.strftime(
		    	'<span class="ic-time"><span>%d</span> <span>days</span></span> <span class="ic-time"><span>%H</span> <span>hours</span></span>  <span class="ic-time"><span>%M</span> <span>minutes</span></span> <span class="ic-time"><span>%S</span> <span>seconds</span></span>'
		    ));
  		});
	}