docs: add doc for TrackByFunction (#27377)

PR Close #27377
2019-01-16 14:40:03 -08:00 · 2019-01-16 14:40:03 -08:00 · 522e4ea898
parent b6819fe9bb
commit 522e4ea898
1 changed files with 1 additions and 3 deletions
--- a/packages/core/src/change_detection/differs/iterable_differs.ts
+++ b/packages/core/src/change_detection/differs/iterable_differs.ts
@ -119,10 +119,8 @@ export interface CollectionChangeRecord<V> extends IterableChangeRecord<V> {}
 /**
 * An optional function passed into the `NgForOf` directive that defines how to track
 * changes for items in an iterable.
+ * The function takes the iteration index and item ID.
 * When supplied, Angular tracks changes by the return value of the function.
- * @param index The iteration index.
- * @param item The item ID.
- * @return The value to use for tracking changes.
 *
 * @publicApi
 */