Added carousel.js for showing/hiding elements

web/src/app/js/carousel.js

@@ -0,0 +1,33 @@
+app.carousel = {
+	hasNext: function(mod, i) {
+		i = i || mod._current;
+		return i < mod._size() - 1;
+	},
+	hasPrev: function(mod, i) {
+		i = i || mod._current;
+		return i > 0;
+	},
+	next: function(mod) {
+		if (!app.carousel.hasNext(mod))
+			return false;
+		return app.carousel.set(mod, mod._current+1);
+	},
+	prev: function(mod) {
+		if (!app.carousel.hasPrev(mod))
+			return false;
+		return app.carousel.set(mod, mod._current-1);
+	},
+	set: function(mod, i) {
+		const elements = mod._elements();
+		const current = elements[mod._current];
+		const next = elements[i];
+		if (mod._animation !== undefined) {
+			// TODO: animation run here
+		}
+		for (var j = 0; j < elements.length; j++)
+			elements[j].style = 'display: none';
+		next.removeAttribute('style');
+		mod._current = i;
+		return true;
+	},
+};