optimization, only declare background creation method once

js/reveal.js

@@ -425,9 +425,64 @@ var Reveal = (function(){
 		dom.background.innerHTML = '';
 		dom.background.classList.add( 'no-transition' );
 
-		// Helper method for creating a background element for the
+		// Iterate over all horizontal slides
-		// given slide
+		toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( slideh ) {
-		function _createBackground( slide, container ) {
+
+			var backgroundStack;
+
+			if( isPrintingPDF() ) {
+				backgroundStack = createBackground( slideh, slideh );
+			}
+			else {
+				backgroundStack = createBackground( slideh, dom.background );
+			}
+
+			// Iterate over all vertical slides
+			toArray( slideh.querySelectorAll( 'section' ) ).forEach( function( slidev ) {
+
+				if( isPrintingPDF() ) {
+					createBackground( slidev, slidev );
+				}
+				else {
+					createBackground( slidev, backgroundStack );
+				}
+
+			} );
+
+		} );
+
+		// Add parallax background if specified
+		if( config.parallaxBackgroundImage ) {
+
+			dom.background.style.backgroundImage = 'url("' + config.parallaxBackgroundImage + '")';
+			dom.background.style.backgroundSize = config.parallaxBackgroundSize;
+
+			// Make sure the below properties are set on the element - these properties are
+			// needed for proper transitions to be set on the element via CSS. To remove
+			// annoying background slide-in effect when the presentation starts, apply
+			// these properties after short time delay
+			setTimeout( function() {
+				dom.wrapper.classList.add( 'has-parallax-background' );
+			}, 1 );
+
+		}
+		else {
+
+			dom.background.style.backgroundImage = '';
+			dom.wrapper.classList.remove( 'has-parallax-background' );
+
+		}
+
+	}
+
+	/**
+	 * Creates a background for the given slide.
+	 *
+	 * @param {HTMLElement} slide
+	 * @param {HTMLElement} container The element that the background
+	 * should be appended to
+	 */
+	function createBackground( slide, container ) {
 
 		var data = {
 			background: slide.getAttribute( 'data-background' ),
@@ -470,56 +525,6 @@ var Reveal = (function(){
 
 	}
 
-		// Iterate over all horizontal slides
-		toArray( document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR ) ).forEach( function( slideh ) {
-
-			var backgroundStack;
-
-			if( isPrintingPDF() ) {
-				backgroundStack = _createBackground( slideh, slideh );
-			}
-			else {
-				backgroundStack = _createBackground( slideh, dom.background );
-			}
-
-			// Iterate over all vertical slides
-			toArray( slideh.querySelectorAll( 'section' ) ).forEach( function( slidev ) {
-
-				if( isPrintingPDF() ) {
-					_createBackground( slidev, slidev );
-				}
-				else {
-					_createBackground( slidev, backgroundStack );
-				}
-
-			} );
-
-		} );
-
-		// Add parallax background if specified
-		if( config.parallaxBackgroundImage ) {
-
-			dom.background.style.backgroundImage = 'url("' + config.parallaxBackgroundImage + '")';
-			dom.background.style.backgroundSize = config.parallaxBackgroundSize;
-
-			// Make sure the below properties are set on the element - these properties are
-			// needed for proper transitions to be set on the element via CSS. To remove
-			// annoying background slide-in effect when the presentation starts, apply
-			// these properties after short time delay
-			setTimeout( function() {
-				dom.wrapper.classList.add( 'has-parallax-background' );
-			}, 1 );
-
-		}
-		else {
-
-			dom.background.style.backgroundImage = '';
-			dom.wrapper.classList.remove( 'has-parallax-background' );
-
-		}
-
-	}
-
 	/**
 	 * Applies the configuration settings from the config
 	 * object. May be called multiple times.