Pass non-plain object values (Date, Map, ...) through in change-case/keys

packages/change-case/src/keys.spec.ts

@@ -71,4 +71,20 @@ describe("change keys", () => {
       expect(camelCase(input, depth, options)).toEqual(result);
     });
   }
+
+  it("passes non-plain object values through unchanged", () => {
+    const date = new Date("2020-01-02T03:04:05.000Z");
+    const map = new Map([["a", 1]]);
+    const regexp = /foo/g;
+    const input = { created_at: date, some_map: map, some_regexp: regexp };
+
+    const result = camelCase(input, Infinity) as Record<string, unknown>;
+
+    expect(result.createdAt).toBe(date);
+    expect((result.createdAt as Date).toISOString()).toBe(
+      "2020-01-02T03:04:05.000Z",
+    );
+    expect(result.someMap).toBe(map);
+    expect(result.someRegexp).toBe(regexp);
+  });
 });

packages/change-case/src/keys.ts

@@ -1,7 +1,14 @@
 import * as changeCase from "./index.js";
 
-const isObject = (object: unknown) =>
-  object !== null && typeof object === "object";
+// Only recurse into arrays and plain objects. Other objects (`Date`, `Map`,
+// `Set`, `RegExp`, class instances, …) can rely on internal slots that a
+// shallow key-renamed clone would not preserve, so they are passed through
+// unchanged as values.
+const isPlainObject = (object: unknown): boolean => {
+  if (object === null || typeof object !== "object") return false;
+  const prototype = Object.getPrototypeOf(object);
+  return prototype === null || prototype === Object.prototype;
+};
 
 function changeKeysFactory<
   Options extends changeCase.Options = changeCase.Options,
@@ -13,12 +20,14 @@ function changeKeysFactory<
     depth = 1,
     options?: Options,
   ): unknown {
-    if (depth === 0 || !isObject(object)) return object;
+    if (depth === 0) return object;
 
     if (Array.isArray(object)) {
       return object.map((item) => changeKeys(item, depth - 1, options));
     }
 
+    if (!isPlainObject(object)) return object;
+
     const result: Record<string, unknown> = Object.create(
       Object.getPrototypeOf(object),
     );