From d57cc8b9da3bce919c3f8e0f6e374d0837c1c05a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timoth=C3=A9e=20=E2=80=9CTim=E2=80=9D=20Pillard?=
 <timothee.pillard@dashlane.com>
Date: Wed, 6 Nov 2024 16:23:10 +0100
Subject: [PATCH 1/2] illustrate incorrect equality check result for non-object
 input types with failing tests

---
 src/__tests__/index.test.ts | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/__tests__/index.test.ts b/src/__tests__/index.test.ts
index cc95854..830c77c 100644
--- a/src/__tests__/index.test.ts
+++ b/src/__tests__/index.test.ts
@@ -146,12 +146,28 @@ describe("shallowEqual on mixed array/objects", () => {
   });
 });
 
+describe("shallowEqual on primitive values of any type", () => {
+  it("should return false", () => {
+    expect(shallowEqual<any>(1, 2)).toBe(false);
+    expect(shallowEqual<any>(1, 1)).toBe(false);
+    expect(shallowEqual<any>("boris", "johnson")).toBe(false);
+    expect(shallowEqual<any>("boris", "boris")).toBe(false);
+  });
+});
+
 describe("shallowEqualObjects", () => {
   objTests.forEach((test) => {
     it("should " + test.should, () => {
       expect(shallowEqualObjects(test.objA, test.objB)).toEqual(test.result);
     });
   });
+
+  it("should return false for primitive values of any type", () => {
+    expect(shallowEqualObjects(1 as any, 2 as any)).toBe(false);
+    expect(shallowEqualObjects(1 as any, 1 as any)).toBe(false);
+    expect(shallowEqualObjects("boris" as any, "johnson" as any)).toBe(false);
+    expect(shallowEqualObjects("boris" as any, "boris" as any)).toBe(false);
+  });
 });
 
 describe("shallowEqualArrays", () => {
@@ -160,4 +176,11 @@ describe("shallowEqualArrays", () => {
       expect(shallowEqualArrays(test.arrA, test.arrB)).toEqual(test.result);
     });
   });
+
+  it("should return false for primitive values of any type", () => {
+    expect(shallowEqualArrays(1 as any, 2 as any)).toBe(false);
+    expect(shallowEqualArrays(1 as any, 1 as any)).toBe(false);
+    expect(shallowEqualArrays("boris" as any, "johnson" as any)).toBe(false);
+    expect(shallowEqualArrays("boris" as any, "boris" as any)).toBe(false);
+  });
 });

From 6d6b67f4b9c82ee016e6921cfba214fee201ee37 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timoth=C3=A9e=20=E2=80=9CTim=E2=80=9D=20Pillard?=
 <timothee.pillard@dashlane.com>
Date: Wed, 6 Nov 2024 16:24:58 +0100
Subject: [PATCH 2/2] suggestion: bail out of shallow comparison if either
 inputs are not of object type

---
 src/__tests__/index.test.ts | 18 +++++++++---------
 src/arrays.ts               |  4 ++++
 src/objects.ts              |  4 ++++
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/__tests__/index.test.ts b/src/__tests__/index.test.ts
index 830c77c..919147b 100644
--- a/src/__tests__/index.test.ts
+++ b/src/__tests__/index.test.ts
@@ -147,11 +147,11 @@ describe("shallowEqual on mixed array/objects", () => {
 });
 
 describe("shallowEqual on primitive values of any type", () => {
-  it("should return false", () => {
+  it("should act correctly", () => {
     expect(shallowEqual<any>(1, 2)).toBe(false);
-    expect(shallowEqual<any>(1, 1)).toBe(false);
+    expect(shallowEqual<any>(1, 1)).toBe(true);
     expect(shallowEqual<any>("boris", "johnson")).toBe(false);
-    expect(shallowEqual<any>("boris", "boris")).toBe(false);
+    expect(shallowEqual<any>("boris", "boris")).toBe(true);
   });
 });
 
@@ -162,11 +162,11 @@ describe("shallowEqualObjects", () => {
     });
   });
 
-  it("should return false for primitive values of any type", () => {
+  it("should act correctly for primitive values of any type", () => {
     expect(shallowEqualObjects(1 as any, 2 as any)).toBe(false);
-    expect(shallowEqualObjects(1 as any, 1 as any)).toBe(false);
+    expect(shallowEqualObjects(1 as any, 1 as any)).toBe(true);
     expect(shallowEqualObjects("boris" as any, "johnson" as any)).toBe(false);
-    expect(shallowEqualObjects("boris" as any, "boris" as any)).toBe(false);
+    expect(shallowEqualObjects("boris" as any, "boris" as any)).toBe(true);
   });
 });
 
@@ -177,10 +177,10 @@ describe("shallowEqualArrays", () => {
     });
   });
 
-  it("should return false for primitive values of any type", () => {
+  it("should act correctly for primitive values of any type", () => {
     expect(shallowEqualArrays(1 as any, 2 as any)).toBe(false);
-    expect(shallowEqualArrays(1 as any, 1 as any)).toBe(false);
+    expect(shallowEqualArrays(1 as any, 1 as any)).toBe(true);
     expect(shallowEqualArrays("boris" as any, "johnson" as any)).toBe(false);
-    expect(shallowEqualArrays("boris" as any, "boris" as any)).toBe(false);
+    expect(shallowEqualArrays("boris" as any, "boris" as any)).toBe(true);
   });
 });
diff --git a/src/arrays.ts b/src/arrays.ts
index e3ff29c..229fb59 100644
--- a/src/arrays.ts
+++ b/src/arrays.ts
@@ -12,6 +12,10 @@ export default function shallowEqualArrays(
     return false;
   }
 
+  if (typeof arrA !== "object" || typeof arrB !== "object") {
+    return false;
+  }
+
   const len = arrA.length;
 
   if (arrB.length !== len) {
diff --git a/src/objects.ts b/src/objects.ts
index 1d37da9..4b0c475 100644
--- a/src/objects.ts
+++ b/src/objects.ts
@@ -12,6 +12,10 @@ export default function shallowEqualObjects<T>(
     return false;
   }
 
+  if (typeof objA !== "object" || typeof objB !== "object") {
+    return false;
+  }
+
   const aKeys = Object.keys(objA);
   const bKeys = Object.keys(objB);
   const len = aKeys.length;