Duck-typing fix. Less `typeof`, more casting.

scripts/script.js

-var url = document.location,
-	linkScreen = document.querySelector('link[title=screen]'),
-	linkProjection = document.querySelector('link[title=projection]'),
-	shower = document.querySelector('div.shower'),
-	slides = document.querySelectorAll('section.slide'),
-	slideList = [], hashList = {},
-	fullscreen = false;
+(function () {
+	var url = document.location,
+		linkScreen = document.querySelector('link[title=screen]'),
+		linkProjection = document.querySelector('link[title=projection]'),
+		shower = document.querySelector('div.shower'),
+		slides = document.querySelectorAll('section.slide'),
+		slideList = [], hashList = {},
+		fullscreen = false;
 
-for(var i = 0, slidesLength = slides.length; i < slidesLength; i++) {
-	var id = slides[i].id;
-	slideList[i] = '#' + id;
-	hashList['#' + id] = i;
-}
+	for(var i = 0, slidesLength = slides.length; i < slidesLength; i++) {
+		var id = slides[i].id;
+		slideList[i] = '#' + id;
+		hashList['#' + id] = i;
+	}
 
-function toggleFull(force) {
-	fullscreen = (typeof force == 'boolean') ? force : (
-		window.fullScreen || // Firefox
-		document.webkitFullScreen || // Webkit
-		screen.width == window.outerWidth && screen.height == window.outerHeight
-	);
-	updateView();
-}
+	function toggleFull(force) {
+		fullscreen = (force != null) ? !!force : (
+			window.fullScreen || // Firefox
+			document.webkitFullScreen || // Webkit
+			screen.width == window.outerWidth && screen.height == window.outerHeight
+		);
+		updateView();
+	}
 
-function turnSlide(e) {
-	if(!fullscreen) return;
-	var current = hashList[url.hash],
-		target;
-	if(e.type == 'keyup') { // Key-Based
-		switch(e.which) {
-			case 33 : // PgUp
-			case 38 : // Up
-			case 37 : // Left
-				current--;
-				break;
-			case 34 : // PgDown
-			case 40 : // Down
-			case 39 : // Right
-				current++;
-				break;
-			case 32 : // Space
-				current += e.shiftKey ? -1 : 1;
-				break;
-			default:
-				return;
+	function turnSlide(e) {
+		if(!fullscreen) return;
+		var current = hashList[url.hash],
+			target;
+		if(e == null) {
+			target = slideList[current++];
+		} else if(e.type == 'keyup') { // Key-Based
+			switch(e.which) {
+				case 33 : // PgUp
+				case 38 : // Up
+				case 37 : // Left
+					current--;
+					break;
+				case 34 : // PgDown
+				case 40 : // Down
+				case 39 : // Right
+					current++;
+					break;
+				case 32 : // Space
+					current += e.shiftKey ? -1 : 1;
+					break;
+				default:
+					return;
+			}
+			target = slideList[current];
+			e.preventDefault();
+		} else { // Specific
+			target = slideList[+e || 0];
 		}
-		target = slideList[current];
-		e.preventDefault();
-	}
-	if(typeof e == 'number') { // Specific
-		target = slideList[e];
+		if(target) url.hash = target;
 	}
-	if(typeof e == 'undefined') { // Next
-		target = slideList[current++];
-	}
-	if(target) url.hash = target;
-}
 
-function updateView() {
-	linkScreen.disabled = fullscreen;
-	linkProjection.disabled = !fullscreen;
-	if(!hashList[url.hash]) turnSlide(0);
-}
+	function updateView() {
+		linkScreen.disabled = fullscreen;
+		linkProjection.disabled = !fullscreen;
+		if(!hashList[url.hash]) turnSlide(0);
+	}
 
-slides[0].addEventListener('click', function(){
-	toggleFull(true);
-}, false);
+	slides[0].addEventListener('click', function(){
+		toggleFull(true);
+	}, false);
 
-document.addEventListener('keyup', turnSlide, false);
-document.addEventListener('keyup', function(e) {
-	if(e.which == 27) toggleFull(false);
-}, false);
+	document.addEventListener('keyup', turnSlide, false);
+	document.addEventListener('keyup', function(e) {
+		if(e.which == 27) toggleFull(false);
+	}, false);
 
-window.addEventListener('resize', toggleFull, false);
-window.addEventListener('DOMContentLoaded', toggleFull, false);
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+	window.addEventListener('resize', toggleFull, false);
+	window.addEventListener('DOMContentLoaded', toggleFull, false);
+})();
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