feat: add isEqual (#396)

* feat: add isEqual

* add test cace

* add should throw error

* add

* add case

* add case

* add case

* add case

* case

* improve

* circular references now return false

* add warning

* console.error test case

* fix case

* case

* fix case

* fix case

* del comment

src/isEqual.ts

@@ -0,0 +1,44 @@
+import warning from './warning';
+
+/**
+ * Deeply compares two object literals.
+ */
+function isEqual(obj1: any, obj2: any): boolean {
+  // https://github.com/mapbox/mapbox-gl-js/pull/5979/files#diff-fde7145050c47cc3a306856efd5f9c3016e86e859de9afbd02c879be5067e58f
+  const refSet = new Set<any>();
+  function deepEqual(a: any, b: any): boolean {
+    const circular = refSet.has(a);
+    warning(!circular, 'Warning: There may be circular references');
+    if (circular) {
+      return false;
+    }
+    if (a === b) {
+      return true;
+    }
+    refSet.add(a);
+    if (Array.isArray(a)) {
+      if (!Array.isArray(b) || a.length !== b.length) {
+        return false;
+      }
+      for (let i = 0; i < a.length; i++) {
+        if (!deepEqual(a[i], b[i])) {
+          return false;
+        }
+      }
+      return true;
+    }
+    if (a && b && typeof a === 'object' && typeof b === 'object') {
+      const keys = Object.keys(a);
+      if (keys.length !== Object.keys(b).length) {
+        return false;
+      }
+      return keys.every(key => deepEqual(a[key], b[key]));
+    }
+    // other
+    return false;
+  }
+
+  return deepEqual(obj1, obj2);
+}
+
+export default isEqual;

src/test/isEqual.test.ts

@@ -0,0 +1,79 @@
+import isEqual from '../isEqual';
+import warning from '../warning';
+
+describe('isEqual', () => {
+  let errorSpy: jest.SpyInstance;
+
+  beforeAll(() => {
+    errorSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    errorSpy.mockReset();
+  });
+
+  afterAll(() => {
+    errorSpy.mockRestore();
+  });
+
+  it('should equal', () => {
+    const valueIsEqual = isEqual(
+      { a: 1, b: 2, c: [1, 2] },
+      { a: 1, b: 2, c: [1, 2] },
+    );
+    expect(valueIsEqual).toBe(true);
+  });
+
+  const obj = { a: 1, b: 2, c: [1, 2], obj: null };
+  it('should equal 2', () => {
+    const valueIsEqual = isEqual(obj, obj);
+    expect(valueIsEqual).toBe(true);
+  });
+
+  it('should not equal', () => {
+    const valueIsEqual = isEqual(
+      { a: 1, b: 2, c: [2, 3] },
+      { a: 1, b: 'x', c: [1, 2] },
+    );
+    expect(valueIsEqual).toBe(false);
+  });
+
+  it('should not equal 2', () => {
+    const valueIsEqual = isEqual(
+      { a: 1, c: [2, 3], b: 2 },
+      { a: 1, c: [1, 2], b: 'x' },
+    );
+    expect(valueIsEqual).toBe(false);
+  });
+
+  it('should not equal 3', () => {
+    const valueIsEqual = isEqual(
+      { a: 1, c: [1, 2], b: 2 },
+      { a: 1, c: [1], b: 'x' },
+    );
+    expect(valueIsEqual).toBe(false);
+  });
+
+  it('should not equal 4', () => {
+    const valueIsEqual = isEqual({ a: 1, b: { c: 2 } }, { a: 1, b: 1 });
+    expect(valueIsEqual).toBe(false);
+  });
+
+  it('should not equal 5', () => {
+    const valueIsEqual = isEqual(
+      { a: 1, b: { c: 2 } },
+      { a: 1, b: { c: 2 }, c: 1 },
+    );
+    expect(valueIsEqual).toBe(false);
+  });
+
+  it('should not equal 6', () => {
+    obj.obj = obj;
+    const obj2 = { a: 1, b: 2, c: [1, 2], obj: null };
+    warning(false, 'error');
+    expect(errorSpy).toHaveBeenCalledWith('Warning: error');
+
+    const valueIsEqual = isEqual(obj, obj2);
+    expect(valueIsEqual).toBe(false);
+  });
+});