From 16b03d18bfac995c2a4bcdc9aad94e4da5725ac5 Mon Sep 17 00:00:00 2001
From: wuyangfan <yangfan.wu@succaiss.com>
Date: Mon, 25 May 2026 17:09:56 +0800
Subject: [PATCH 1/2] fix: check FormData before buffer in isJSONSerializable

Closes #580
---
 src/utils.ts       |  6 +++---
 test/index.test.ts | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/utils.ts b/src/utils.ts
index a773431b..f8d3afdf 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -28,14 +28,14 @@ export function isJSONSerializable(value: any): boolean {
   if (Array.isArray(value)) {
     return true;
   }
-  if (value.buffer) {
-    return false;
-  }
   // `FormData` and `URLSearchParams` should't have a `toJSON` method,
   // but Bun adds it, which is non-standard.
   if (value instanceof FormData || value instanceof URLSearchParams) {
     return false;
   }
+  if (value.buffer) {
+    return false;
+  }
   return (
     (value.constructor && value.constructor.name === "Object") ||
     typeof value.toJSON === "function"
diff --git a/test/index.test.ts b/test/index.test.ts
index 5ac20b07..3b2eb1a6 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -525,3 +525,21 @@ describe("ofetch", () => {
     });
   });
 });
+
+describe("isJSONSerializable", () => {
+  let isJSONSerializable: (value: unknown) => boolean;
+
+  beforeAll(async () => {
+    const utils = await import("../src/utils.ts");
+    isJSONSerializable = utils.isJSONSerializable;
+  });
+
+  it("returns false for FormData and URLSearchParams before buffer checks", () => {
+    expect(isJSONSerializable(new FormData())).toBe(false);
+    expect(isJSONSerializable(new URLSearchParams())).toBe(false);
+
+    const data = new FormData();
+    data.append("foo", "bar");
+    expect(isJSONSerializable(data)).toBe(false);
+  });
+});

From 9c657a9afca222abcfcbe35ef48a335504397533 Mon Sep 17 00:00:00 2001
From: wuyangfan <yangfan.wu@succaiss.com>
Date: Tue, 26 May 2026 09:40:20 +0800
Subject: [PATCH 2/2] fix: handle null in isJSONSerializable and check FormData
 first

Treat null as JSON-serializable via explicit check (typeof null is
"object") and probe FormData/URLSearchParams before value.buffer.

Fixes #571
Fixes #580
---
 src/utils.ts       | 5 ++++-
 test/index.test.ts | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/utils.ts b/src/utils.ts
index f8d3afdf..ff7871a0 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -18,8 +18,11 @@ export function isJSONSerializable(value: any): boolean {
   if (value === undefined) {
     return false;
   }
+  if (value === null) {
+    return true;
+  }
   const t = typeof value;
-  if (t === "string" || t === "number" || t === "boolean" || t === null) {
+  if (t === "string" || t === "number" || t === "boolean") {
     return true;
   }
   if (t !== "object") {
diff --git a/test/index.test.ts b/test/index.test.ts
index 3b2eb1a6..c3f7a848 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -542,4 +542,8 @@ describe("isJSONSerializable", () => {
     data.append("foo", "bar");
     expect(isJSONSerializable(data)).toBe(false);
   });
+
+  it("returns true for null without throwing", () => {
+    expect(isJSONSerializable(null)).toBe(true); // eslint-disable-line unicorn/no-null
+  });
 });