suggestion: validate inputs being of type object, early bail-out if necessary

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 act correctly", () => {
+    expect(shallowEqual<any>(1, 2)).toBe(false);
+    expect(shallowEqual<any>(1, 1)).toBe(true);
+    expect(shallowEqual<any>("boris", "johnson")).toBe(false);
+    expect(shallowEqual<any>("boris", "boris")).toBe(true);
+  });
+});
+
 describe("shallowEqualObjects", () => {
   objTests.forEach((test) => {
     it("should " + test.should, () => {
       expect(shallowEqualObjects(test.objA, test.objB)).toEqual(test.result);
     });
   });
+
+  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(true);
+    expect(shallowEqualObjects("boris" as any, "johnson" as any)).toBe(false);
+    expect(shallowEqualObjects("boris" as any, "boris" as any)).toBe(true);
+  });
 });
 
 describe("shallowEqualArrays", () => {
@@ -160,4 +176,11 @@ describe("shallowEqualArrays", () => {
       expect(shallowEqualArrays(test.arrA, test.arrB)).toEqual(test.result);
     });
   });
+
+  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(true);
+    expect(shallowEqualArrays("boris" as any, "johnson" as any)).toBe(false);
+    expect(shallowEqualArrays("boris" as any, "boris" as any)).toBe(true);
+  });
 });

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) {

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;