don't overwrite existing classes on slides (closes #23)

diff --git a/js/reveal.js b/js/reveal.js
index 736545c647425fc738dcd1134bbe456fb5e714ee..ba2cfd5ecabe7d5b337197d615a851ff963a4bc2 100644 (file)
--- a/js/reveal.js
+++ b/js/reveal.js
@@ -428,8 +428,6 @@ var Reveal = (function(){
                if( slides.length ) {
                        // Enforce max and minimum index bounds
                        index = Math.max(Math.min(index, slides.length - 1), 0);
-                       
-                       slides[index].className = 'present';
 
                        for( var i = 0; i < slides.length; i++ ) {
                                var slide = slides[i];
@@ -440,20 +438,27 @@ var Reveal = (function(){
                                        slide.style.display = Math.abs( index - i ) > 3 ? 'none' : 'block';
                                }
 
+                               slides[i].classList.remove( 'past' );
+                               slides[i].classList.remove( 'present' );
+                               slides[i].classList.remove( 'future' );
+
                                if( i < index ) {
                                        // Any element previous to index is given the 'past' class
-                                       slide.className = 'past';
+                                       slides[i].classList.add( 'past' );
                                }
                                else if( i > index ) {
                                        // Any element subsequent to index is given the 'future' class
-                                       slide.className = 'future';
+                                       slides[i].classList.add( 'future' );
                                }
 
                                // If this element contains vertical slides
                                if( slide.querySelector( 'section' ) ) {
-                                       slide.classList.add( 'stack' );
+                                       slides[i].classList.add( 'stack' );
                                }
                        }
+
+                       // Mark the current slide as present
+                       slides[index].classList.add( 'present' );
                }
                else {
                        // Since there are no slides we can't be anywhere beyond the