list: indexOf

src/vs/base/browser/ui/list/listView.ts

@@ -602,6 +602,10 @@ export class ListView<T> implements ISpliceable<T>, IDisposable {
 		return this.items[index].element;
 	}
 
+	indexOf(element: T): number {
+		return this.items.findIndex(item => item.element === element);
+	}
+
 	domElement(index: number): HTMLElement | null {
 		const row = this.items[index].row;
 		return row && row.domNode;

src/vs/base/browser/ui/list/listWidget.ts

@@ -1323,6 +1323,10 @@ export class List<T> implements ISpliceable<T>, IThemable, IDisposable {
 		return this.view.element(index);
 	}
 
+	indexOf(element: T): number {
+		return this.view.indexOf(element);
+	}
+
 	get length(): number {
 		return this.view.length;
 	}