Switch some typeof to hasOWnProperty checks

diff --git a/js/game.js b/js/game.js
index 9aa62fe..a34c312 100644
--- a/js/game.js
+++ b/js/game.js
@@ -532,7 +532,7 @@ class Location
         for (const content_area of content_areas) {
             let content = elt(content_area);
             if (content_area == 'main-nav') {
-                if (typeof (content.originalHTML) === 'undefined') {
+                if (!content.hasOwnProperty("originalHTML")) {
                     content.originalHTML = content.innerHTML;
                 }
                 content.innerHTML = interpolateVariables(content.originalHTML);
@@ -693,6 +693,11 @@ class Game
      * @type {number}
      */
     tick = 0;
+    /**
+     * Whether this particular game has a nav bar
+     * @type {boolean}
+     */
+    hasNavBar;
     /**
      * The list of all Game Object's managed by the FRISE script. An object
      * can be used to represent a thing such as a person, tool, piece of
@@ -759,7 +764,7 @@ class Game
      * tag in the HTML file for the game. If this tag is not present, the
      * game will not have a main navigation bar and menu.
      */
-    initializesMainNavGameContentArea()
+    initializeMainNavGameContentArea()
     {
         let body_objs = tag("body");
         if (body_objs[0] === undefined) {
@@ -775,8 +780,10 @@ class Game
         let main_nav_objs = tag("x-main-nav");
         if (typeof main_nav_objs[0] === "undefined") {
             game_screen.innerHTML = `<div id="game-content"></div>`;
+            this.hasNavBar = false;
             return;
         }
+        this.hasNavBar = true;
         let main_nav_obj = main_nav_objs[0];
         let history_buttons;
         if (is_right_to_left) {
@@ -854,11 +861,11 @@ class Game
         this.locations = xtag("x-location");
         for (const oid in this.objects) {
             let object = this.objects[oid];
-            if (typeof object.position !== 'undefined') {
+            if (object.hasOwnProperty("position")) {
                 let location_name = object.position;
-                if (typeof this.locations[location_name] !== 'undefined') {
+                if (this.locations.hasOwnProperty(location_name)) {
                     let location = this.locations[location_name]
-                    if (typeof location.items == "undefined") {
+                    if (!location.hasOwnProperty("items")) {
                         location.items = [];
                     }
                     location.items.push(object.id);
@@ -911,7 +918,7 @@ class Game
         let old_objects = this.objects;
         this.objects = game_state.objects;
         for (const field in old_objects) {
-            if (typeof this.objects[field] === 'undefined') {
+            if (!this.objects.hasOwnProperty(field)) {
                 /* we assume our game never deletes objects or locations, so
                    if we find an object in old_objects (presumably coming
                    from a more recently parse HTML file) that was not
@@ -919,9 +926,9 @@ class Game
                  */
                 this.objects[field] = old_objects[field];
             } else {
-                if (typeof old_objects['action'] !== 'undefined') {
+                if (old_objects.hasOwnProperty('action')) {
                     this.objects['action'] = old_objects['action'];
-                } else if (typeof this.objects['action'] !== 'undefined') {
+                } else if (this.objects.hasOwnProperty('action')) {
                     delete this.objects['action'];
                 }
             }
@@ -931,7 +938,7 @@ class Game
         let location;
         this.locations = {};
         for (const location_name in old_locations) {
-            if (typeof locations[location_name] === 'undefined') {
+            if (!locations.hasOwnProperty(location_name)) {
                 location = old_locations[location_name];
             } else {
                 let location_object = locations[location_name];
@@ -940,8 +947,8 @@ class Game
                     location[field] = location_object[field];
                     if (field == 'present' || field == 'action' ||
                         field == 'default-action') {
-                        if (typeof old_locations[location_name][field] ===
-                            'undefined') {
+                        if (!old_locations[
+                            location_name].hasOwnProperty(field)) {
                             delete location[field];
                         } else {
                             location[field] =
@@ -1095,7 +1102,7 @@ class Game
     {
         let i = 1;
         let saves_location = game.locations['saves'];
-        while (typeof saves_location['filename' + i] !== 'undefined') {
+        while (saves_location.hasOwnProperty('filename' + i)) {
             this.deleteSlot(i);
             i++;
         }
@@ -1167,12 +1174,14 @@ class Game
      */
     takeTurn(hash)
     {
-        if (hash == "#previous") {
-            this.previousHistory();
-            return;
-        } else if (hash == "#next") {
-            this.nextHistory();
-            return;
+        if (this.hasNavBar) {
+            if (hash == "#previous") {
+                this.previousHistory();
+                return;
+            } else if (hash == "#next") {
+                this.nextHistory();
+                return;
+            }
         }
         let new_game_state;
         if (sessionStorage.current) {
@@ -1182,7 +1191,9 @@ class Game
             return;
         }
         this.future_history = [];
-        elt('next-history').disabled = true;
+        if (this.hasNavBar) {
+            elt('next-history').disabled = true;
+        }
         if (sessionStorage.current) {
             this.history.push(new_game_state);
         }
@@ -1190,10 +1201,12 @@ class Game
         this.evaluateDefaultActions(this.locations);
         sessionStorage.current = this.captureState();
         this.describeMainCharacterLocation();
-        if (this.history.length == 0) {
-            elt('previous-history').disabled = true;
-        } else {
-            elt('previous-history').disabled = false;
+        if (this.hasNavBar) {
+            if (this.history.length == 0) {
+                elt('previous-history').disabled = true;
+            } else {
+                elt('previous-history').disabled = false;
+            }
         }
     }
     /**
@@ -1225,7 +1238,7 @@ class Game
         if (!move_object || !this.locations[destination_id]) {
             return false;
         }
-        if (typeof move_object.position !== 'undefined') {
+        if (move_object.hasOwnProperty("position")) {
             let old_position = move_object.position;
             let old_location = this.locations[old_position];
             old_location.items.filter((value) => {