LibWeb/IDB: Implement iterate_a_cursor

Author: https://github.com/stelar7
Commit: 98d08b27e4
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4524
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/IndexedDB/IDBIndex.cpp

@@ -101,4 +101,19 @@ JS::Value IDBIndex::key_path() const
         });
 }
 
+// https://w3c.github.io/IndexedDB/#index-referenced-value
+HTML::SerializationRecord IDBIndex::get_referenced_value(IndexRecord const& index_record) const
+{
+    // Records in an index are said to have a referenced value.
+    // This is the value of the record in the index’s referenced object store which has a key equal to the index’s record’s value.
+    return m_index
+        ->object_store()
+        ->records()
+        .first_matching([&](auto const& store_record) {
+            return Key::equals(store_record.key, index_record.value);
+        })
+        .value()
+        .value;
+}
+
 }