add check into the utility isEqual for comparision of functions by reference (#63)

Author: inpokon

src/is/__tests__/equal.ts

@@ -29,7 +29,16 @@ describe('utils/is/equal', () => {
     });
 
     it('equal objects', () => {
+        const obj = {
+            f: () => {}
+        };
+        const obj2 = {
+            f: () => {}
+        }
         expect(isEqual({}, {})).toBe(true);
+        expect(isEqual(obj, obj)).toBe(true);
+        expect(isEqual(obj, obj2)).toBe(false);
+        expect(isEqual({ f: () => {} }, { f: () => {} })).toBe(false);
         expect(isEqual({ a: 1 }, { a: 1 })).toBe(true);
         expect(isEqual({ a: 1 }, { a: 2 })).toBe(false);
         expect(isEqual({ a: 1, b: [1, 2, { c: 3 }] }, { a: 1, b: [1, 2, { c: 3 }] })).toBe(true);
@@ -45,4 +54,14 @@ describe('utils/is/equal', () => {
         expect(isEqual({}, 5)).toBe(false);
         expect(isEqual(3, 'test')).toBe(false);
     });
+
+    it('equal function', () => {
+        const f = () => {};
+        const f2 = () => {};
+
+        expect(isEqual(f, f)).toBe(true);
+        expect(isEqual(f, f2)).toBe(false);
+        expect(isEqual(() => {}, () => {})).toBe(false);
+        expect(isEqual(() => {}, function () {})).toBe(false);
+    });
 });

src/is/equal.ts

@@ -70,6 +70,10 @@ const isEqual = (test1, test2): boolean => {
         return isEqualObjects(test1, test2);
     }
 
+    if (typeof test1 === 'function') {
+        return test1 === test2;
+    }
+
     return isEqualNativeTypes(test1, test2);
 };