test("length is 2", () => { expect(Reflect.deleteProperty).toHaveLength(2); }); describe("errors", () => { test("target must be an object", () => { [null, undefined, "foo", 123, NaN, Infinity].forEach(value => { expect(() => { Reflect.deleteProperty(value); }).toThrowWithMessage(TypeError, `${value} is not an object`); }); }); }); describe("normal behavior", () => { test("deleting non-existent property", () => { expect(Reflect.deleteProperty({})).toBeTrue(); expect(Reflect.deleteProperty({}, "foo")).toBeTrue(); }); test("deleting existent property", () => { var o = { foo: 1 }; expect(o.foo).toBe(1); expect(Reflect.deleteProperty(o, "foo")).toBeTrue(); expect(o.foo).toBeUndefined(); expect(Reflect.deleteProperty(o, "foo")).toBeTrue(); expect(o.foo).toBeUndefined(); }); test("deleting existent, configurable, non-writable property", () => { var o = {}; Object.defineProperty(o, "foo", { value: 1, configurable: true, writable: false }); expect(Reflect.deleteProperty(o, "foo")).toBeTrue(); expect(o.foo).toBeUndefined(); }); test("deleting existent, non-configurable, writable property", () => { var o = {}; Object.defineProperty(o, "foo", { value: 1, configurable: false, writable: true }); expect(Reflect.deleteProperty(o, "foo")).toBeFalse(); expect(o.foo).toBe(1); }); test("deleting existent, non-configurable, non-writable property", () => { var o = {}; Object.defineProperty(o, "foo", { value: 1, configurable: false, writable: false }); expect(Reflect.deleteProperty(o, "foo")).toBeFalse(); expect(o.foo).toBe(1); }); test("deleting array index", () => { var a = [1, 2, 3]; expect(a).toHaveLength(3); expect(a[0]).toBe(1); expect(a[1]).toBe(2); expect(a[2]).toBe(3); expect(Reflect.deleteProperty(a, 1)).toBeTrue(); expect(a).toHaveLength(3); expect(a[0]).toBe(1); expect(a[1]).toBeUndefined(); expect(a[2]).toBe(3); }); });