function loadSlide()

in js/reveal.js [3740:3851]
42 lines of code
10 McCabe index (conditional complexity)

	function loadSlide( slide, options ) {

		options = options || {};

		// Show the slide element
		slide.style.display = config.display;

		// Media elements with data-src attributes
		toArray( slide.querySelectorAll( 'img[data-src], video[data-src], audio[data-src], iframe[data-src]' ) ).forEach( function( element ) {
			if( element.tagName !== 'IFRAME' || shouldPreload( element ) ) {
				element.setAttribute( 'src', element.getAttribute( 'data-src' ) );
				element.setAttribute( 'data-lazy-loaded', '' );
				element.removeAttribute( 'data-src' );
			}
		} );

		// Media elements with <source> children
		toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( media ) {
			var sources = 0;

			toArray( media.querySelectorAll( 'source[data-src]' ) ).forEach( function( source ) {
				source.setAttribute( 'src', source.getAttribute( 'data-src' ) );
				source.removeAttribute( 'data-src' );
				source.setAttribute( 'data-lazy-loaded', '' );
				sources += 1;
			} );

			// If we rewrote sources for this video/audio element, we need
			// to manually tell it to load from its new origin
			if( sources > 0 ) {
				media.load();
			}
		} );


		// Show the corresponding background element
		var background = slide.slideBackgroundElement;
		if( background ) {
			background.style.display = 'block';

			var backgroundContent = slide.slideBackgroundContentElement;

			// If the background contains media, load it
			if( background.hasAttribute( 'data-loaded' ) === false ) {
				background.setAttribute( 'data-loaded', 'true' );

				var backgroundImage = slide.getAttribute( 'data-background-image' ),
					backgroundVideo = slide.getAttribute( 'data-background-video' ),
					backgroundVideoLoop = slide.hasAttribute( 'data-background-video-loop' ),
					backgroundVideoMuted = slide.hasAttribute( 'data-background-video-muted' ),
					backgroundIframe = slide.getAttribute( 'data-background-iframe' );

				// Images
				if( backgroundImage ) {
					backgroundContent.style.backgroundImage = 'url('+ encodeURI( backgroundImage ) +')';
				}
				// Videos
				else if ( backgroundVideo && !isSpeakerNotes() ) {
					var video = document.createElement( 'video' );

					if( backgroundVideoLoop ) {
						video.setAttribute( 'loop', '' );
					}

					if( backgroundVideoMuted ) {
						video.muted = true;
					}

					// Inline video playback works (at least in Mobile Safari) as
					// long as the video is muted and the `playsinline` attribute is
					// present
					if( isMobileDevice ) {
						video.muted = true;
						video.autoplay = true;
						video.setAttribute( 'playsinline', '' );
					}

					// Support comma separated lists of video sources
					backgroundVideo.split( ',' ).forEach( function( source ) {
						video.innerHTML += '<source src="'+ source +'">';
					} );

					backgroundContent.appendChild( video );
				}
				// Iframes
				else if( backgroundIframe && options.excludeIframes !== true ) {
					var iframe = document.createElement( 'iframe' );
					iframe.setAttribute( 'allowfullscreen', '' );
					iframe.setAttribute( 'mozallowfullscreen', '' );
					iframe.setAttribute( 'webkitallowfullscreen', '' );

					// Only load autoplaying content when the slide is shown to
					// avoid having it play in the background
					if( /autoplay=(1|true|yes)/gi.test( backgroundIframe ) ) {
						iframe.setAttribute( 'data-src', backgroundIframe );
					}
					else {
						iframe.setAttribute( 'src', backgroundIframe );
					}

					iframe.style.width  = '100%';
					iframe.style.height = '100%';
					iframe.style.maxHeight = '100%';
					iframe.style.maxWidth = '100%';

					backgroundContent.appendChild( iframe );
				}
			}

		}

	}