Moves full screen functions in UIUtil

modules/UI/UI.js

 /**
  * Toggles the application in and out of full screen mode
  * (a.k.a. presentation mode in Chrome).
- * @see https://developer.mozilla.org/en-US/docs/Web/API/Fullscreen_API
  */
 UI.toggleFullScreen = function() {
-    let isFullScreen = document.fullscreenElement
-            || document.mozFullScreenElement // current working methods
-            || document.webkitFullscreenElement
-            || document.msFullscreenElement;
-
-    if (isFullScreen) {
-        if (document.exitFullscreen) {
-            document.exitFullscreen();
-        } else if (document.msExitFullscreen) {
-            document.msExitFullscreen();
-        } else if (document.mozCancelFullScreen) {
-            document.mozCancelFullScreen();
-        } else if (document.webkitExitFullscreen) {
-            document.webkitExitFullscreen();
-        }
-    } else {
-        if (document.documentElement.requestFullscreen) {
-            document.documentElement.requestFullscreen();
-        } else if (document.documentElement.msRequestFullscreen) {
-            document.documentElement.msRequestFullscreen();
-        } else if (document.documentElement.mozRequestFullScreen) {
-            document.documentElement.mozRequestFullScreen();
-        } else if (document.documentElement.webkitRequestFullscreen) {
-            document.documentElement
-                .webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);
-        }
-    }
+    (UIUtil.isFullScreen())
+        ? UIUtil.exitFullScreen()
+        : UIUtil.enterFullScreen();
 };
 
 /**
     $(document).on(
         'webkitfullscreenchange mozfullscreenchange fullscreenchange',
         () => {
-            let isFullScreen = document.fullscreenElement
-                || document.mozFullScreenElement
-                || document.webkitFullscreenElement
-                || document.msFullscreenElement;
-
-            eventEmitter.emit(UIEvents.FULLSCREEN_TOGGLED, isFullScreen);
+            eventEmitter.emit(  UIEvents.FULLSCREEN_TOGGLED,
+                                UIUtil.isFullScreen());
 
             onResize();
         }

modules/UI/util/UIUtil.js

          window.location.href = url;
     },
 
-     isFullScreen () {
-         return document.fullScreen
-             || document.mozFullScreen
-             || document.webkitIsFullScreen;
-     },
+    /**
+     * Indicates if we're currently in full screen mode.
+     *
+     * @return {boolean} {true} to indicate that we're currently in full screen
+     * mode, {false} otherwise
+     */
+    isFullScreen() {
+        return document.fullscreenElement
+            || document.mozFullScreenElement
+            || document.webkitFullscreenElement
+            || document.msFullscreenElement;
+    },
+
+    /**
+     * Exits full screen mode.
+     * @see https://developer.mozilla.org/en-US/docs/Web/API/Fullscreen_API
+     */
+    exitFullScreen() {
+        if (document.exitFullscreen) {
+            document.exitFullscreen();
+        } else if (document.msExitFullscreen) {
+            document.msExitFullscreen();
+        } else if (document.mozCancelFullScreen) {
+            document.mozCancelFullScreen();
+        } else if (document.webkitExitFullscreen) {
+            document.webkitExitFullscreen();
+        }
+    },
+
+    /**
+     * Enter full screen mode.
+     * @see https://developer.mozilla.org/en-US/docs/Web/API/Fullscreen_API
+     */
+    enterFullScreen() {
+        if (document.documentElement.requestFullscreen) {
+            document.documentElement.requestFullscreen();
+        } else if (document.documentElement.msRequestFullscreen) {
+            document.documentElement.msRequestFullscreen();
+        } else if (document.documentElement.mozRequestFullScreen) {
+            document.documentElement.mozRequestFullScreen();
+        } else if (document.documentElement.webkitRequestFullscreen) {
+            document.documentElement
+                .webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);
+        }
+    },
 
-     /**
+    /**
       * Create html attributes string out of object properties.
       * @param {Object} attrs object with properties
       * @returns {String} string of html element attributes