Improve dispoable listener functions

src/utils/Dom.ts

@@ -0,0 +1,26 @@
+import { IDisposable } from "../Interfaces";
+
+/**
+ * Adds a disposabe listener to a node in the DOM, returning the disposable.
+ * @param type The event type.
+ * @param handler The handler for the listener.
+ */
+export function addDisposableListener(
+  node: Element | Window | Document,
+  type: string,
+  handler: (e: any) => void,
+  useCapture?: boolean
+): IDisposable {
+  node.addEventListener(type, handler, useCapture);
+  return {
+    dispose: () => {
+      if (!handler) {
+        // Already disposed
+        return;
+      }
+      node.removeEventListener(type, handler, useCapture);
+      node = null;
+      handler = null;
+    }
+  };
+}