Convert mergeMap.js to ts

src/matrix/e2ee/RoomEncryption.js

@@ -16,7 +16,7 @@ limitations under the License.
 
 import {MEGOLM_ALGORITHM, DecryptionSource} from "./common.js";
 import {groupEventsBySession} from "./megolm/decryption/utils";
-import {mergeMap} from "../../utils/mergeMap.js";
+import {mergeMap} from "../../utils/mergeMap";
 import {groupBy} from "../../utils/groupBy";
 import {makeTxnId} from "../common.js";
 

src/matrix/e2ee/megolm/decryption/DecryptionPreparation.js

@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import {DecryptionChanges} from "./DecryptionChanges.js";
-import {mergeMap} from "../../../../utils/mergeMap.js";
+import {mergeMap} from "../../../../utils/mergeMap";
 
 /**
  * Class that contains all the state loaded from storage to decrypt the given events

src/utils/mergeMap.ts

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-export function mergeMap(src, dst) {
+export function mergeMap<K, V>(src: Map<K, V> | undefined, dst: Map<K, V>) {
     if (src) {
         for (const [key, value] of src.entries()) {
             dst.set(key, value);