Captions and titles

I want to show just captions in lightbox, and title only when captions are missing. When i change code from

var s = '';
if (title != '') {s = '<span id="titleText">' + title + '</span>';}
if (caption != '') {
		if (title != ''){
		s += '<br />';
		}
s += '<span id="captionText">' + caption +'</span>';}

to

var s = '';
if (caption != '') {s = '<span id="captionText">' + caption + </span>';		}
if (caption = ''&&title != '') {s += '<span id="titleText">' + title +'</span>';

I get what I want on single images, but then there’s nothing on slideshow images. What am I missing? `

https://wordpress.org/plugins/wp-jquery-lightbox/