From 2dd0215108df0300584371adc4ce2b654095d469 Mon Sep 17 00:00:00 2001
From: landuoduo <vv22345@163.com>
Date: Tue, 7 Jul 2026 11:57:03 +0800
Subject: [PATCH] fix: treat null as JSON-serializable in isJSONSerializable

typeof null is "object", so the t === null branch was dead code (t is
always a string). isJSONSerializable(null) fell through to value.buffer
and threw "Cannot read properties of null". null is JSON-serializable,
so check value === null and return true instead.

Resolves #571
---
 src/utils.ts       |  2 +-
 test/index.test.ts | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/utils.ts b/src/utils.ts
index a773431b..eca6b351 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -19,7 +19,7 @@ export function isJSONSerializable(value: any): boolean {
     return false;
   }
   const t = typeof value;
-  if (t === "string" || t === "number" || t === "boolean" || t === null) {
+  if (value === null || t === "string" || t === "number" || t === "boolean") {
     return true;
   }
   if (t !== "object") {
diff --git a/test/index.test.ts b/test/index.test.ts
index 5ac20b07..7c54d608 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -10,6 +10,7 @@ import {
 import { Readable } from "node:stream";
 import { H3, HTTPError, readBody, serve } from "h3";
 import { $fetch } from "../src/index.ts";
+import { isJSONSerializable } from "../src/utils.ts";
 
 describe("ofetch", () => {
   let listener: ReturnType<typeof serve>;
@@ -525,3 +526,24 @@ describe("ofetch", () => {
     });
   });
 });
+
+describe("isJSONSerializable", () => {
+  it("treats null as serializable without throwing", () => {
+    // `typeof null` is "object", so the old `t === null` check was dead code
+    // and execution fell through to `value.buffer`, throwing on null.
+    // eslint-disable-next-line unicorn/no-null
+    const value = null;
+    expect(() => isJSONSerializable(value)).not.toThrow();
+    expect(isJSONSerializable(value)).toBe(true);
+  });
+
+  it("classifies common values", () => {
+    expect(isJSONSerializable(undefined)).toBe(false);
+    expect(isJSONSerializable("str")).toBe(true);
+    expect(isJSONSerializable(1)).toBe(true);
+    expect(isJSONSerializable({ a: 1 })).toBe(true);
+    expect(isJSONSerializable([1, 2])).toBe(true);
+    expect(isJSONSerializable(new Uint8Array())).toBe(false);
+    expect(isJSONSerializable(() => {})).toBe(false);
+  });
+});