ladybird/Libraries/LibJS/Tests/operators/delete-basic.js

test("deleting object properties", () => {
  const o = {};
  o.x = 1;
  o.y = 2;
  o.z = 3;
  expect(Object.getOwnPropertyNames(o)).toHaveLength(3);

  expect(delete o.x).toBeTrue();
  expect(o.hasOwnProperty("x")).toBeFalse();
  expect(o.hasOwnProperty("y")).toBeTrue();
  expect(o.hasOwnProperty("z")).toBeTrue();
  expect(Object.getOwnPropertyNames(o)).toHaveLength(2);

  expect(delete o.y).toBeTrue();
  expect(o.hasOwnProperty("x")).toBeFalse();
  expect(o.hasOwnProperty("y")).toBeFalse();
  expect(o.hasOwnProperty("z")).toBeTrue();
  expect(Object.getOwnPropertyNames(o)).toHaveLength(1);

  expect(delete o.z).toBeTrue();
  expect(o.hasOwnProperty("x")).toBeFalse();
  expect(o.hasOwnProperty("y")).toBeFalse();
  expect(o.hasOwnProperty("z")).toBeFalse();
  expect(Object.getOwnPropertyNames(o)).toHaveLength(0);
});

test("deleting array indices", () => {
  const a = [3, 5, 7];

  expect(Object.getOwnPropertyNames(a)).toHaveLength(4);

  expect(delete a[0]).toBeTrue();
  expect(a.hasOwnProperty(0)).toBeFalse();
  expect(a.hasOwnProperty(1)).toBeTrue();
  expect(a.hasOwnProperty(2)).toBeTrue();
  expect(Object.getOwnPropertyNames(a)).toHaveLength(3);

  expect(delete a[1]).toBeTrue();
  expect(a.hasOwnProperty(0)).toBeFalse();
  expect(a.hasOwnProperty(1)).toBeFalse();
  expect(a.hasOwnProperty(2)).toBeTrue();
  expect(Object.getOwnPropertyNames(a)).toHaveLength(2);

  expect(delete a[2]).toBeTrue();
  expect(a.hasOwnProperty(0)).toBeFalse();
  expect(a.hasOwnProperty(1)).toBeFalse();
  expect(a.hasOwnProperty(2)).toBeFalse();
  expect(Object.getOwnPropertyNames(a)).toHaveLength(1);
});

test("deleting non-configurable property", () => {
  const q = {};
  Object.defineProperty(q, "foo", { value: 1, writable: false, enumerable: false });
  expect(q.foo).toBe(1);

  expect(delete q.foo).toBeFalse();
  expect(q.hasOwnProperty("foo")).toBeTrue();
});