slides three or more steps away from current are now hidden

diff --git a/js/reveal.js b/js/reveal.js
index 79437aed511d15c4eddd85b07004b395c72df84b..3dddf7d06970556ab3ac466068bddb040b5a52f9 100644 (file)
--- a/js/reveal.js
+++ b/js/reveal.js
@@ -282,16 +282,23 @@ var Reveal = (function(){
                        index = Math.max(Math.min(index, slides.length - 1), 0);
                        
                        slides[index].setAttribute('class', 'present');
-                       
-                       // Any element previous to index is given the 'past' class
-                       slides.slice(0, index).map(function(element){
-                               element.setAttribute('class', 'past');
-                       });
-                       
-                       // Any element subsequent to index is given the 'future' class
-                       slides.slice(index + 1).map(function(element){
-                               element.setAttribute('class', 'future');
-                       });
+
+                       for( var i = 0; i < slides.length; i++ ) {
+                               var slide = slides[i];
+
+                               // Optimization; hide all slides that are three or more steps 
+                               // away from the present slide
+                               slide.style.display = Math.abs( index - i ) > 3 ? 'none' : 'block';
+
+                               if( i < index ) {
+                                       // Any element previous to index is given the 'past' class
+                                       slide.setAttribute('class', 'past');
+                               }
+                               else if( i > index ) {
+                                       // Any element subsequent to index is given the 'future' class
+                                       slide.setAttribute('class', 'future');
+                               }
+                       }
                }
                else {
                        // Since there are no slides we can't be anywhere beyond the