reveal.js

// Restart GIFs (doesn't work in Firefox)
			if( /\.gif/i.test( backgroundImageURL ) ) {
				var searchstring = '.gif?currenttime=';
				var timestamp = Math.floor(Date.now() / 1000)
				var position = backgroundImageURL.indexOf(searchstring);
				if(position !== -1) {
					var oldtimestamp = backgroundImageURL.substr(position + searchstring.length, timestamp.length);
					backgroundImageURL = backgroundImageURL.replace(oldtimestamp,timestamp);
				}
				else {
					backgroundImageURL = backgroundImageURL.replace('.gif', searchstring + timestamp);
				}

				currentBackground.style.backgroundImage = backgroundImageURL;
			}