feat(butil): add beforeUnload support to Butil #6169 (#6170)

src/Butil/Bit.Butil.Demo/Pages/WindowPage.razor

@@ -16,18 +16,29 @@
 }
 </pre>
 
-<h3>Open the DevTools and start pressing keys on your keyboard</h3>
+<br />
+<hr />
+<br />
 
-<button @onclick=AddEventListener>AddEventListener</button>
-&nbsp;
-<button @onclick=RemoveEventListener>RemoveEventListener</button>
+<h4>Open the DevTools and start pressing keys on your keyboard</h4>
+<br />
+<button @onclick=AddEventListener>AddEventListener</button>&nbsp;<button @onclick=RemoveEventListener>RemoveEventListener</button>
+<br />
+<br />
+<div>Is KeyDown Registered? @isKeyDownRegistered</div>
 
+<br />
 <hr />
+<br />
 
-<div>Is Registered: @isRegistered</div>
+<button @onclick=AddBeforeUnload>AddBeforeUnload</button>&nbsp;<button @onclick=RemoveBeforeUnload>RemoveBeforeUnload</button>
+<br />
+<br />
+<div>Is BeforeUnload Registered? @isBeforeUnloadRegistered</div>
 
 @code {
-    private bool isRegistered = false;
+    private bool isKeyDownRegistered;
+    private bool isBeforeUnloadRegistered;
 
     private Action<ButilKeyboardEventArgs> _handler = default!;
 
@@ -41,12 +52,24 @@
     private void AddEventListener()
     {
         _ = window.AddEventListener(ButilEvents.KeyDown, _handler);
-        isRegistered = true;
+        isKeyDownRegistered = true;
     }
 
     private void RemoveEventListener()
     {
         _ = window.RemoveEventListener(ButilEvents.KeyDown, _handler);
-        isRegistered = false;
+        isKeyDownRegistered = false;
+    }
+
+    private void AddBeforeUnload()
+    {
+        _ = window.AddBeforeUnload();
+        isBeforeUnloadRegistered = true;
+    }
+
+    private void RemoveBeforeUnload()
+    {
+        _ = window.RemoveBeforeUnload();
+        isBeforeUnloadRegistered = false;
     }
 }

src/Butil/Bit.Butil/Internals/JsInterops/WindowJsInterop.cs

@@ -0,0 +1,17 @@
+using System.Threading.Tasks;
+using Microsoft.JSInterop;
+
+namespace Bit.Butil;
+
+internal static class WindowJsInterop
+{
+    internal static async Task AddBeforeUnload(this IJSRuntime js)
+    {
+        await js.InvokeVoidAsync("BitButil.window.addBeforeUnload");
+    }
+
+    internal static async Task RemoveBeforeUnload(this IJSRuntime js)
+    {
+        await js.InvokeVoidAsync("BitButil.window.removeBeforeUnload");
+    }
+}

src/Butil/Bit.Butil/Publics/Window.cs

@@ -17,4 +17,14 @@ public async Task RemoveEventListener<T>(string domEvent, Action<T> listener, bo
     {
         await DomEventDispatcher.RemoveEventListener(js, ElementName, domEvent, listener, useCapture);
     }
+
+    public async Task AddBeforeUnload()
+    {
+        await js.AddBeforeUnload();
+    }
+
+    public async Task RemoveBeforeUnload()
+    {
+        await js.RemoveBeforeUnload();
+    }
 }

src/Butil/Bit.Butil/Scripts/window.ts

@@ -0,0 +1,20 @@
+var BitButil = BitButil || {};
+
+(function (butil: any) {
+    butil.window = {
+        addBeforeUnload,
+        removeBeforeUnload
+    };
+
+    function addBeforeUnload() {
+        window.onbeforeunload = e => {
+            e.preventDefault();
+            e.returnValue = true;
+            return true;
+        };
+    }
+
+    function removeBeforeUnload() {
+        window.onbeforeunload = null;
+    }
+}(BitButil));