add geolocation demo to demonstrate running async JavaScript

website/more_documentation/run_javascript_documentation.py

@@ -1,5 +1,7 @@
 from nicegui import ui
 
+from ..documentation_tools import text_demo
+
 
 def main_demo() -> None:
     async def alert():
@@ -16,3 +18,34 @@ def main_demo() -> None:
     ui.button('receive result', on_click=get_date)
     ui.button('access elements', on_click=access_elements)
     label = ui.label()
+
+
+def more() -> None:
+    @text_demo('Run async JavaScript', '''
+        Using `run_javascript` you can also run asynchronous code in the browser.
+        The following demo shows how to get the current location of the user.
+    ''')
+    def run_async_javascript():
+        async def show_location():
+            response = await ui.run_javascript('''
+                return await new Promise((resolve, reject) => {
+                    if (!navigator.geolocation) {
+                        reject(new Error('Geolocation is not supported by your browser'));
+                    } else {
+                        navigator.geolocation.getCurrentPosition(
+                            (position) => {
+                                resolve({
+                                    latitude: position.coords.latitude,
+                                    longitude: position.coords.longitude,
+                                });
+                            },
+                            () => {
+                                reject(new Error('Unable to retrieve your location'));
+                            }
+                        );
+                    }
+                });
+            ''', timeout=5.0)
+            ui.notify(f'Your location is {response["latitude"]}, {response["longitude"]}')
+
+        ui.button('Show location', on_click=show_location)