use const event

lib/Timeline.js

@@ -40,11 +40,12 @@ let Timeline = class Timeline extends lit_element_1.LitElement {
         this._clearSelectionHandler = (_e) => {
             this.clearSelectedItems();
             window.removeEventListener("click", this._clearSelectionHandler);
-            this.dispatchEvent(new CustomEvent("item-selected", {
+            const myEvent = new CustomEvent("item-selected", {
                 detail: { items: this.selectedList },
                 bubbles: true,
                 composed: true,
-            }));
+            });
+            this.dispatchEvent(myEvent);
         };
         this.rows = [];
         this.items = [];

src/Timeline.ts

@@ -598,13 +598,12 @@ class Timeline extends LitElement {
   private _clearSelectionHandler = (_e: MouseEvent) => {
     this.clearSelectedItems();
     window.removeEventListener("click", this._clearSelectionHandler);
-    this.dispatchEvent(
-      new CustomEvent("item-selected", {
-        detail: { items: this.selectedList },
-        bubbles: true,
-        composed: true,
-      })
-    );
+    const myEvent = new CustomEvent("item-selected", {
+      detail: { items: this.selectedList },
+      bubbles: true,
+      composed: true,
+    });
+    this.dispatchEvent(myEvent);
   };
   private _getEventClickHandler(clickedItem: Selectable) {
     const item = clickedItem;