diff --git a/integration/batching-with-context/batching.ts b/integration/batching-with-context/batching.ts
index 30968e1ec..4da12298a 100644
--- a/integration/batching-with-context/batching.ts
+++ b/integration/batching-with-context/batching.ts
@@ -236,12 +236,10 @@ export const BatchMapQueryResponse = {
 
   fromJSON(object: any): BatchMapQueryResponse {
     const message = { ...baseBatchMapQueryResponse } as BatchMapQueryResponse;
-    message.entities = {};
-    if (object.entities !== undefined && object.entities !== null) {
-      Object.entries(object.entities).forEach(([key, value]) => {
-        message.entities[key] = Entity.fromJSON(value);
-      });
-    }
+    message.entities = Object.entries(object.entities ?? {}).reduce<{ [key: string]: Entity }>((acc, [key, value]) => {
+      acc[key] = Entity.fromJSON(value);
+      return acc;
+    }, {});
     return message;
   },
 
@@ -258,14 +256,12 @@ export const BatchMapQueryResponse = {
 
   fromPartial(object: DeepPartial<BatchMapQueryResponse>): BatchMapQueryResponse {
     const message = { ...baseBatchMapQueryResponse } as BatchMapQueryResponse;
-    message.entities = {};
-    if (object.entities !== undefined && object.entities !== null) {
-      Object.entries(object.entities).forEach(([key, value]) => {
-        if (value !== undefined) {
-          message.entities[key] = Entity.fromPartial(value);
-        }
-      });
-    }
+    message.entities = Object.entries(object.entities ?? {}).reduce<{ [key: string]: Entity }>((acc, [key, value]) => {
+      if (value !== undefined) {
+        acc[key] = Entity.fromPartial(value);
+      }
+      return acc;
+    }, {});
     return message;
   },
 };
diff --git a/integration/batching/batching.ts b/integration/batching/batching.ts
index 9eef7d4c8..1aa547719 100644
--- a/integration/batching/batching.ts
+++ b/integration/batching/batching.ts
@@ -234,12 +234,10 @@ export const BatchMapQueryResponse = {
 
   fromJSON(object: any): BatchMapQueryResponse {
     const message = { ...baseBatchMapQueryResponse } as BatchMapQueryResponse;
-    message.entities = {};
-    if (object.entities !== undefined && object.entities !== null) {
-      Object.entries(object.entities).forEach(([key, value]) => {
-        message.entities[key] = Entity.fromJSON(value);
-      });
-    }
+    message.entities = Object.entries(object.entities ?? {}).reduce<{ [key: string]: Entity }>((acc, [key, value]) => {
+      acc[key] = Entity.fromJSON(value);
+      return acc;
+    }, {});
     return message;
   },
 
@@ -256,14 +254,12 @@ export const BatchMapQueryResponse = {
 
   fromPartial(object: DeepPartial<BatchMapQueryResponse>): BatchMapQueryResponse {
     const message = { ...baseBatchMapQueryResponse } as BatchMapQueryResponse;
-    message.entities = {};
-    if (object.entities !== undefined && object.entities !== null) {
-      Object.entries(object.entities).forEach(([key, value]) => {
-        if (value !== undefined) {
-          message.entities[key] = Entity.fromPartial(value);
-        }
-      });
-    }
+    message.entities = Object.entries(object.entities ?? {}).reduce<{ [key: string]: Entity }>((acc, [key, value]) => {
+      if (value !== undefined) {
+        acc[key] = Entity.fromPartial(value);
+      }
+      return acc;
+    }, {});
     return message;
   },
 };
diff --git a/integration/simple-long/simple.ts b/integration/simple-long/simple.ts
index 55dfae0da..95c7eda7a 100644
--- a/integration/simple-long/simple.ts
+++ b/integration/simple-long/simple.ts
@@ -211,24 +211,27 @@ export const SimpleWithMap = {
 
   fromJSON(object: any): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
-        message.nameLookup[key] = String(value);
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
-        message.intLookup[Number(key)] = Number(value);
-      });
-    }
-    message.longLookup = {};
-    if (object.longLookup !== undefined && object.longLookup !== null) {
-      Object.entries(object.longLookup).forEach(([key, value]) => {
-        message.longLookup[key] = Long.fromString(value as string);
-      });
-    }
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
+        acc[key] = String(value);
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Number(value);
+        return acc;
+      },
+      {}
+    );
+    message.longLookup = Object.entries(object.longLookup ?? {}).reduce<{ [key: string]: Long }>(
+      (acc, [key, value]) => {
+        acc[key] = Long.fromString(value as string);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -257,30 +260,33 @@ export const SimpleWithMap = {
 
   fromPartial(object: DeepPartial<SimpleWithMap>): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.nameLookup[key] = String(value);
+          acc[key] = String(value);
         }
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.intLookup[Number(key)] = Number(value);
+          acc[Number(key)] = Number(value);
         }
-      });
-    }
-    message.longLookup = {};
-    if (object.longLookup !== undefined && object.longLookup !== null) {
-      Object.entries(object.longLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.longLookup = Object.entries(object.longLookup ?? {}).reduce<{ [key: string]: Long }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.longLookup[key] = Long.fromValue(value);
+          acc[key] = Long.fromValue(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/simple-optionals/simple.ts b/integration/simple-optionals/simple.ts
index f3b9af737..6108c6ad8 100644
--- a/integration/simple-optionals/simple.ts
+++ b/integration/simple-optionals/simple.ts
@@ -892,24 +892,27 @@ export const SimpleWithMap = {
 
   fromJSON(object: any): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
-        message.entitiesById[Number(key)] = Entity.fromJSON(value);
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
-        message.nameLookup[key] = String(value);
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
-        message.intLookup[Number(key)] = Number(value);
-      });
-    }
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
+        acc[key] = String(value);
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Number(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -938,30 +941,33 @@ export const SimpleWithMap = {
 
   fromPartial(object: DeepPartial<SimpleWithMap>): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entitiesById[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.nameLookup[key] = String(value);
+          acc[key] = String(value);
         }
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.intLookup[Number(key)] = Number(value);
+          acc[Number(key)] = Number(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
@@ -1168,12 +1174,13 @@ export const SimpleWithSnakeCaseMap = {
 
   fromJSON(object: any): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
-        message.entitiesById[Number(key)] = Entity.fromJSON(value);
-      });
-    }
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -1190,14 +1197,15 @@ export const SimpleWithSnakeCaseMap = {
 
   fromPartial(object: DeepPartial<SimpleWithSnakeCaseMap>): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entitiesById[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/simple-snake/simple.ts b/integration/simple-snake/simple.ts
index 0dea90a41..4ce1a42aa 100644
--- a/integration/simple-snake/simple.ts
+++ b/integration/simple-snake/simple.ts
@@ -892,24 +892,27 @@ export const SimpleWithMap = {
 
   fromJSON(object: any): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
-        message.entitiesById[Number(key)] = Entity.fromJSON(value);
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
-        message.nameLookup[key] = String(value);
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
-        message.intLookup[Number(key)] = Number(value);
-      });
-    }
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
+        acc[key] = String(value);
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Number(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -938,30 +941,33 @@ export const SimpleWithMap = {
 
   fromPartial(object: DeepPartial<SimpleWithMap>): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entitiesById[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.nameLookup[key] = String(value);
+          acc[key] = String(value);
         }
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.intLookup[Number(key)] = Number(value);
+          acc[Number(key)] = Number(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
@@ -1168,12 +1174,13 @@ export const SimpleWithSnakeCaseMap = {
 
   fromJSON(object: any): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entities_by_id = {};
-    if (object.entities_by_id !== undefined && object.entities_by_id !== null) {
-      Object.entries(object.entities_by_id).forEach(([key, value]) => {
-        message.entities_by_id[Number(key)] = Entity.fromJSON(value);
-      });
-    }
+    message.entities_by_id = Object.entries(object.entities_by_id ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -1190,14 +1197,15 @@ export const SimpleWithSnakeCaseMap = {
 
   fromPartial(object: DeepPartial<SimpleWithSnakeCaseMap>): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entities_by_id = {};
-    if (object.entities_by_id !== undefined && object.entities_by_id !== null) {
-      Object.entries(object.entities_by_id).forEach(([key, value]) => {
+    message.entities_by_id = Object.entries(object.entities_by_id ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entities_by_id[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/simple-unrecognized-enum/simple.ts b/integration/simple-unrecognized-enum/simple.ts
index 2de1a45ef..d5d6ac01b 100644
--- a/integration/simple-unrecognized-enum/simple.ts
+++ b/integration/simple-unrecognized-enum/simple.ts
@@ -883,24 +883,27 @@ export const SimpleWithMap = {
 
   fromJSON(object: any): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
-        message.entitiesById[Number(key)] = Entity.fromJSON(value);
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
-        message.nameLookup[key] = String(value);
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
-        message.intLookup[Number(key)] = Number(value);
-      });
-    }
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
+        acc[key] = String(value);
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Number(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -929,30 +932,33 @@ export const SimpleWithMap = {
 
   fromPartial(object: DeepPartial<SimpleWithMap>): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entitiesById[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.nameLookup[key] = String(value);
+          acc[key] = String(value);
         }
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.intLookup[Number(key)] = Number(value);
+          acc[Number(key)] = Number(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
@@ -1159,12 +1165,13 @@ export const SimpleWithSnakeCaseMap = {
 
   fromJSON(object: any): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
-        message.entitiesById[Number(key)] = Entity.fromJSON(value);
-      });
-    }
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -1181,14 +1188,15 @@ export const SimpleWithSnakeCaseMap = {
 
   fromPartial(object: DeepPartial<SimpleWithSnakeCaseMap>): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entitiesById[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/simple/simple.ts b/integration/simple/simple.ts
index f2329834f..93d273821 100644
--- a/integration/simple/simple.ts
+++ b/integration/simple/simple.ts
@@ -1035,48 +1035,54 @@ export const SimpleWithMap = {
 
   fromJSON(object: any): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
-        message.entitiesById[Number(key)] = Entity.fromJSON(value);
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
-        message.nameLookup[key] = String(value);
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
-        message.intLookup[Number(key)] = Number(value);
-      });
-    }
-    message.mapOfTimestamps = {};
-    if (object.mapOfTimestamps !== undefined && object.mapOfTimestamps !== null) {
-      Object.entries(object.mapOfTimestamps).forEach(([key, value]) => {
-        message.mapOfTimestamps[key] = fromJsonTimestamp(value);
-      });
-    }
-    message.mapOfBytes = {};
-    if (object.mapOfBytes !== undefined && object.mapOfBytes !== null) {
-      Object.entries(object.mapOfBytes).forEach(([key, value]) => {
-        message.mapOfBytes[key] = bytesFromBase64(value as string);
-      });
-    }
-    message.mapOfStringValues = {};
-    if (object.mapOfStringValues !== undefined && object.mapOfStringValues !== null) {
-      Object.entries(object.mapOfStringValues).forEach(([key, value]) => {
-        message.mapOfStringValues[key] = value as string | undefined;
-      });
-    }
-    message.longLookup = {};
-    if (object.longLookup !== undefined && object.longLookup !== null) {
-      Object.entries(object.longLookup).forEach(([key, value]) => {
-        message.longLookup[Number(key)] = Number(value);
-      });
-    }
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
+        acc[key] = String(value);
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Number(value);
+        return acc;
+      },
+      {}
+    );
+    message.mapOfTimestamps = Object.entries(object.mapOfTimestamps ?? {}).reduce<{ [key: string]: Date }>(
+      (acc, [key, value]) => {
+        acc[key] = fromJsonTimestamp(value);
+        return acc;
+      },
+      {}
+    );
+    message.mapOfBytes = Object.entries(object.mapOfBytes ?? {}).reduce<{ [key: string]: Uint8Array }>(
+      (acc, [key, value]) => {
+        acc[key] = bytesFromBase64(value as string);
+        return acc;
+      },
+      {}
+    );
+    message.mapOfStringValues = Object.entries(object.mapOfStringValues ?? {}).reduce<{
+      [key: string]: string | undefined;
+    }>((acc, [key, value]) => {
+      acc[key] = value as string | undefined;
+      return acc;
+    }, {});
+    message.longLookup = Object.entries(object.longLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Number(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -1129,62 +1135,68 @@ export const SimpleWithMap = {
 
   fromPartial(object: DeepPartial<SimpleWithMap>): SimpleWithMap {
     const message = { ...baseSimpleWithMap } as SimpleWithMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entitiesById[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
-    message.nameLookup = {};
-    if (object.nameLookup !== undefined && object.nameLookup !== null) {
-      Object.entries(object.nameLookup).forEach(([key, value]) => {
-        if (value !== undefined) {
-          message.nameLookup[key] = String(value);
-        }
-      });
-    }
-    message.intLookup = {};
-    if (object.intLookup !== undefined && object.intLookup !== null) {
-      Object.entries(object.intLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.nameLookup = Object.entries(object.nameLookup ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.intLookup[Number(key)] = Number(value);
+          acc[key] = String(value);
         }
-      });
-    }
-    message.mapOfTimestamps = {};
-    if (object.mapOfTimestamps !== undefined && object.mapOfTimestamps !== null) {
-      Object.entries(object.mapOfTimestamps).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.intLookup = Object.entries(object.intLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.mapOfTimestamps[key] = value;
+          acc[Number(key)] = Number(value);
         }
-      });
-    }
-    message.mapOfBytes = {};
-    if (object.mapOfBytes !== undefined && object.mapOfBytes !== null) {
-      Object.entries(object.mapOfBytes).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.mapOfTimestamps = Object.entries(object.mapOfTimestamps ?? {}).reduce<{ [key: string]: Date }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.mapOfBytes[key] = value;
+          acc[key] = value;
         }
-      });
-    }
-    message.mapOfStringValues = {};
-    if (object.mapOfStringValues !== undefined && object.mapOfStringValues !== null) {
-      Object.entries(object.mapOfStringValues).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.mapOfBytes = Object.entries(object.mapOfBytes ?? {}).reduce<{ [key: string]: Uint8Array }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.mapOfStringValues[key] = value;
+          acc[key] = value;
         }
-      });
-    }
-    message.longLookup = {};
-    if (object.longLookup !== undefined && object.longLookup !== null) {
-      Object.entries(object.longLookup).forEach(([key, value]) => {
+        return acc;
+      },
+      {}
+    );
+    message.mapOfStringValues = Object.entries(object.mapOfStringValues ?? {}).reduce<{
+      [key: string]: string | undefined;
+    }>((acc, [key, value]) => {
+      if (value !== undefined) {
+        acc[key] = value;
+      }
+      return acc;
+    }, {});
+    message.longLookup = Object.entries(object.longLookup ?? {}).reduce<{ [key: number]: number }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.longLookup[Number(key)] = Number(value);
+          acc[Number(key)] = Number(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
@@ -1618,12 +1630,13 @@ export const SimpleWithSnakeCaseMap = {
 
   fromJSON(object: any): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
-        message.entitiesById[Number(key)] = Entity.fromJSON(value);
-      });
-    }
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = Entity.fromJSON(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -1640,14 +1653,15 @@ export const SimpleWithSnakeCaseMap = {
 
   fromPartial(object: DeepPartial<SimpleWithSnakeCaseMap>): SimpleWithSnakeCaseMap {
     const message = { ...baseSimpleWithSnakeCaseMap } as SimpleWithSnakeCaseMap;
-    message.entitiesById = {};
-    if (object.entitiesById !== undefined && object.entitiesById !== null) {
-      Object.entries(object.entitiesById).forEach(([key, value]) => {
+    message.entitiesById = Object.entries(object.entitiesById ?? {}).reduce<{ [key: number]: Entity }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.entitiesById[Number(key)] = Entity.fromPartial(value);
+          acc[Number(key)] = Entity.fromPartial(value);
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
@@ -1742,12 +1756,13 @@ export const SimpleWithMapOfEnums = {
 
   fromJSON(object: any): SimpleWithMapOfEnums {
     const message = { ...baseSimpleWithMapOfEnums } as SimpleWithMapOfEnums;
-    message.enumsById = {};
-    if (object.enumsById !== undefined && object.enumsById !== null) {
-      Object.entries(object.enumsById).forEach(([key, value]) => {
-        message.enumsById[Number(key)] = value as number;
-      });
-    }
+    message.enumsById = Object.entries(object.enumsById ?? {}).reduce<{ [key: number]: StateEnum }>(
+      (acc, [key, value]) => {
+        acc[Number(key)] = value as number;
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -1764,14 +1779,15 @@ export const SimpleWithMapOfEnums = {
 
   fromPartial(object: DeepPartial<SimpleWithMapOfEnums>): SimpleWithMapOfEnums {
     const message = { ...baseSimpleWithMapOfEnums } as SimpleWithMapOfEnums;
-    message.enumsById = {};
-    if (object.enumsById !== undefined && object.enumsById !== null) {
-      Object.entries(object.enumsById).forEach(([key, value]) => {
+    message.enumsById = Object.entries(object.enumsById ?? {}).reduce<{ [key: number]: StateEnum }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.enumsById[Number(key)] = value as number;
+          acc[Number(key)] = value as number;
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/struct/google/protobuf/struct.ts b/integration/struct/google/protobuf/struct.ts
index d54b6ca9b..20465f053 100644
--- a/integration/struct/google/protobuf/struct.ts
+++ b/integration/struct/google/protobuf/struct.ts
@@ -126,12 +126,13 @@ export const Struct = {
 
   fromJSON(object: any): Struct {
     const message = { ...baseStruct } as Struct;
-    message.fields = {};
-    if (object.fields !== undefined && object.fields !== null) {
-      Object.entries(object.fields).forEach(([key, value]) => {
-        message.fields[key] = value as any | undefined;
-      });
-    }
+    message.fields = Object.entries(object.fields ?? {}).reduce<{ [key: string]: any | undefined }>(
+      (acc, [key, value]) => {
+        acc[key] = value as any | undefined;
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -148,14 +149,15 @@ export const Struct = {
 
   fromPartial(object: DeepPartial<Struct>): Struct {
     const message = { ...baseStruct } as Struct;
-    message.fields = {};
-    if (object.fields !== undefined && object.fields !== null) {
-      Object.entries(object.fields).forEach(([key, value]) => {
+    message.fields = Object.entries(object.fields ?? {}).reduce<{ [key: string]: any | undefined }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.fields[key] = value;
+          acc[key] = value;
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/use-date-string/use-date-string.ts b/integration/use-date-string/use-date-string.ts
index 57bf66733..d7e15656f 100644
--- a/integration/use-date-string/use-date-string.ts
+++ b/integration/use-date-string/use-date-string.ts
@@ -85,12 +85,13 @@ export const Todo = {
       object.optionalTimestamp !== undefined && object.optionalTimestamp !== null
         ? String(object.optionalTimestamp)
         : undefined;
-    message.mapOfTimestamps = {};
-    if (object.mapOfTimestamps !== undefined && object.mapOfTimestamps !== null) {
-      Object.entries(object.mapOfTimestamps).forEach(([key, value]) => {
-        message.mapOfTimestamps[key] = String(value);
-      });
-    }
+    message.mapOfTimestamps = Object.entries(object.mapOfTimestamps ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
+        acc[key] = String(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -119,14 +120,15 @@ export const Todo = {
     message.timestamp = object.timestamp ?? undefined;
     message.repeatedTimestamp = (object.repeatedTimestamp ?? []).map((e) => e);
     message.optionalTimestamp = object.optionalTimestamp ?? undefined;
-    message.mapOfTimestamps = {};
-    if (object.mapOfTimestamps !== undefined && object.mapOfTimestamps !== null) {
-      Object.entries(object.mapOfTimestamps).forEach(([key, value]) => {
+    message.mapOfTimestamps = Object.entries(object.mapOfTimestamps ?? {}).reduce<{ [key: string]: string }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.mapOfTimestamps[key] = value;
+          acc[key] = value;
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/use-date-true/use-date-true.ts b/integration/use-date-true/use-date-true.ts
index d820bf767..172e251c7 100644
--- a/integration/use-date-true/use-date-true.ts
+++ b/integration/use-date-true/use-date-true.ts
@@ -85,12 +85,13 @@ export const Todo = {
       object.optionalTimestamp !== undefined && object.optionalTimestamp !== null
         ? fromJsonTimestamp(object.optionalTimestamp)
         : undefined;
-    message.mapOfTimestamps = {};
-    if (object.mapOfTimestamps !== undefined && object.mapOfTimestamps !== null) {
-      Object.entries(object.mapOfTimestamps).forEach(([key, value]) => {
-        message.mapOfTimestamps[key] = fromJsonTimestamp(value);
-      });
-    }
+    message.mapOfTimestamps = Object.entries(object.mapOfTimestamps ?? {}).reduce<{ [key: string]: Date }>(
+      (acc, [key, value]) => {
+        acc[key] = fromJsonTimestamp(value);
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -119,14 +120,15 @@ export const Todo = {
     message.timestamp = object.timestamp ?? undefined;
     message.repeatedTimestamp = (object.repeatedTimestamp ?? []).map((e) => e);
     message.optionalTimestamp = object.optionalTimestamp ?? undefined;
-    message.mapOfTimestamps = {};
-    if (object.mapOfTimestamps !== undefined && object.mapOfTimestamps !== null) {
-      Object.entries(object.mapOfTimestamps).forEach(([key, value]) => {
+    message.mapOfTimestamps = Object.entries(object.mapOfTimestamps ?? {}).reduce<{ [key: string]: Date }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.mapOfTimestamps[key] = value;
+          acc[key] = value;
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/integration/value/google/protobuf/struct.ts b/integration/value/google/protobuf/struct.ts
index d54b6ca9b..20465f053 100644
--- a/integration/value/google/protobuf/struct.ts
+++ b/integration/value/google/protobuf/struct.ts
@@ -126,12 +126,13 @@ export const Struct = {
 
   fromJSON(object: any): Struct {
     const message = { ...baseStruct } as Struct;
-    message.fields = {};
-    if (object.fields !== undefined && object.fields !== null) {
-      Object.entries(object.fields).forEach(([key, value]) => {
-        message.fields[key] = value as any | undefined;
-      });
-    }
+    message.fields = Object.entries(object.fields ?? {}).reduce<{ [key: string]: any | undefined }>(
+      (acc, [key, value]) => {
+        acc[key] = value as any | undefined;
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 
@@ -148,14 +149,15 @@ export const Struct = {
 
   fromPartial(object: DeepPartial<Struct>): Struct {
     const message = { ...baseStruct } as Struct;
-    message.fields = {};
-    if (object.fields !== undefined && object.fields !== null) {
-      Object.entries(object.fields).forEach(([key, value]) => {
+    message.fields = Object.entries(object.fields ?? {}).reduce<{ [key: string]: any | undefined }>(
+      (acc, [key, value]) => {
         if (value !== undefined) {
-          message.fields[key] = value;
+          acc[key] = value;
         }
-      });
-    }
+        return acc;
+      },
+      {}
+    );
     return message;
   },
 };
diff --git a/src/main.ts b/src/main.ts
index 3f2436aae..e9f196a9e 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1082,15 +1082,14 @@ function generateFromJson(ctx: Context, fullName: string, messageDesc: Descripto
     // and then use the snippet to handle repeated fields if necessary
     if (isRepeated(field)) {
       if (isMapType(ctx, messageDesc, field)) {
-        chunks.push(code`message.${fieldName} = {};`);
-        chunks.push(code`if (object.${fieldName} !== undefined && object.${fieldName} !== null) {`);
+        const fieldType = toTypeName(ctx, messageDesc, field);
         const i = maybeCastToNumber(ctx, messageDesc, field, 'key');
         chunks.push(code`
-          Object.entries(object.${fieldName}).forEach(([key, value]) => {
-            message.${fieldName}[${i}] = ${readSnippet('value')};
-          });
+          message.${fieldName} = Object.entries(object.${fieldName} ?? {}).reduce<${fieldType}>((acc, [key, value]) => {
+            acc[${i}] = ${readSnippet('value')};
+            return acc;
+          }, {});
         `);
-        chunks.push(code`}`);
       } else if (isAnyValueType(field)) {
         chunks.push(code`
           message.${fieldName} = Array.isArray(object?.${fieldName}) ? [...object.${fieldName}] : [];
@@ -1303,17 +1302,16 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
     // and then use the snippet to handle repeated fields if necessary
     if (isRepeated(field)) {
       if (isMapType(ctx, messageDesc, field)) {
-        chunks.push(code`message.${fieldName} = {};`);
-        chunks.push(code`if (object.${fieldName} !== undefined && object.${fieldName} !== null) {`);
+        const fieldType = toTypeName(ctx, messageDesc, field);
         const i = maybeCastToNumber(ctx, messageDesc, field, 'key');
         chunks.push(code`
-          Object.entries(object.${fieldName}).forEach(([key, value]) => {
+          message.${fieldName} = Object.entries(object.${fieldName} ?? {}).reduce<${fieldType}>((acc, [key, value]) => {
             if (value !== undefined) {
-              message.${fieldName}[${i}] = ${readSnippet('value')};
+              acc[${i}] = ${readSnippet('value')};
             }
-          });
+            return acc;
+          }, {});
         `);
-        chunks.push(code`}`);
       } else {
         chunks.push(code`
           message.${fieldName} = (object.${fieldName} ?? []).map((e) => ${readSnippet('e')});