Fix nested map issue

serializer.test.ts

@@ -78,6 +78,9 @@ it("serializes simple objects", () => {
   expect(result["d"].has(2)).toBe(false);
   expect(result["e"].get("z")).toBe(8);
   expect(result["e"].get("k")).toBeUndefined();
+
+  checkReversability(new Set(["a", new Set([1, "b"])]));
+  checkReversability(new Map([["a", new Map([[1, "test"]])]]));
 });
 
 it("restores objects constructed from class", () => {

serializer.ts

@@ -184,33 +184,49 @@ function crawl(
   }
 
   if (obj !== undefined && obj !== null && typeof obj != "function") {
-    let result = callback(obj);
+    const result = callback(obj);
 
     if (result === STOP_CRAWLING) {
       return;
     }
 
     if (Array.isArray(obj)) {
-      let subresult = obj.map((value) => crawl(value, callback, replace, memo));
+      const subresult = obj.map((value) =>
+        crawl(value, callback, replace, memo)
+      );
       if (replace) {
         subresult.forEach((value, index) => {
           obj[index] = value;
         });
       }
     } else if (obj instanceof Set) {
-      let subresult = new Set();
-      for (let item of obj) {
+      const subresult = new Set();
+      for (const item of obj) {
         subresult.add(crawl(item, callback, replace, memo));
       }
       if (replace) {
         obj.clear();
-        for (let item of subresult) {
+        for (const item of subresult) {
           obj.add(item);
         }
       }
+    } else if (obj instanceof Map) {
+      const subresult = new Map();
+      for (const [key, item] of obj.entries()) {
+        subresult.set(
+          crawl(key, callback, replace, memo),
+          crawl(item, callback, replace, memo),
+        );
+      }
+      if (replace) {
+        obj.clear();
+        for (const [key, item] of subresult.entries()) {
+          obj.set(key, item);
+        }
+      }
     } else if (obj instanceof Object) {
-      let subresult: any = {};
-      for (let key in obj) {
+      const subresult: any = {};
+      for (const key in obj) {
         subresult[key] = crawl(obj[key], callback, replace, memo);
       }
       if (replace) {