ladybird/Libraries/LibJS/Tests/functions/function-rest-params.js

test("rest parameter with no arguments", () => {
  function foo(...a) {
    expect(a).toBeInstanceOf(Array);
    expect(a).toHaveLength(0);
  }
  foo();
});

test("rest parameter with arguments", () => {
  function foo(...a) {
    expect(a).toEqual(["foo", 123, undefined, { foo: "bar" }]);
  }
  foo("foo", 123, undefined, { foo: "bar" });
});

test("rest parameter after normal parameters with no arguments", () => {
  function foo(a, b, ...c) {
    expect(a).toBe("foo");
    expect(b).toBe(123);
    expect(c).toEqual([]);
  }
  foo("foo", 123);
});

test("rest parameter after normal parameters with arguments", () => {
  function foo(a, b, ...c) {
    expect(a).toBe("foo");
    expect(b).toBe(123);
    expect(c).toEqual([undefined, { foo: "bar" }]);
  }
  foo("foo", 123, undefined, { foo: "bar" });
});

test("basic arrow function rest parameters", () => {
  let foo = (...a) => {
    expect(a).toBeInstanceOf(Array);
    expect(a).toHaveLength(0);
  };
  foo();

  foo = (a, b, ...c) => {
    expect(a).toBe("foo");
    expect(b).toBe(123);
    expect(c).toEqual([undefined, { foo: "bar" }]);
  };
  foo("foo", 123, undefined, { foo: "bar" });
});