Return the same console object for a window

src/AngleSharp.Js.Tests/DomTests.cs

@@ -68,5 +68,19 @@ public async Task NumericIndexerOfTokenListYieldsTheToken()
             var result = await "new DOMParser().parseFromString(`<div class='a b'></div>`, 'text/html').body.firstChild.classList[1]".EvalScriptAsync();
             Assert.AreEqual("b", result);
         }
+
+        [Test]
+        public async Task ConsoleIsTheSameObjectOnEveryAccess()
+        {
+            var result = await "window.console === window.console".EvalScriptAsync();
+            Assert.AreEqual("True", result);
+        }
+
+        [Test]
+        public async Task ConsoleKeepsPropertiesAssignedToIt()
+        {
+            var result = await "(function () { window.console.marker = 'kept'; return window.console.marker; })()".EvalScriptAsync();
+            Assert.AreEqual("kept", result);
+        }
     }
 }

src/AngleSharp.Js/Dom/WindowExtensions.cs

@@ -7,13 +7,17 @@ namespace AngleSharp.Js.Dom
     using AngleSharp.Html.Dom;
     using AngleSharp.Js.Attributes;
     using System;
+    using System.Runtime.CompilerServices;
 
     /// <summary>
     /// Defines a set of extensions for the window object.
     /// </summary>
     [DomExposed("Window")]
     public static class WindowExtensions
     {
+        private static readonly ConditionalWeakTable<IWindow, Console> Consoles =
+            new ConditionalWeakTable<IWindow, Console>();
+
         /// <summary>
         /// Posts a message.
         /// </summary>
@@ -34,15 +38,17 @@ public static void PostMessage(this IWindow window, String message, String targe
         public static IWindow Top(this IWindow window) => window.Document.Context?.Creator?.DefaultView;
 
         /// <summary>
-        /// Gets the console instance.
+        /// Gets the console instance. The same instance is returned for the same
+        /// window, so that `window.console === window.console` holds and anything
+        /// script puts on the console is still there on the next access.
         /// </summary>
         /// <param name="window"></param>
         /// <returns></returns>
         [DomName("console")]
         [DomAccessor(Accessors.Getter)]
         public static Console Console(this IWindow window)
         {
-            return new Console(window);
+            return Consoles.GetValue(window, w => new Console(w));
         }
 
         /// <summary>