ladybird/Libraries/LibJS/Tests/builtins/Function/Function.js

describe("correct behavior", () => {
  test("constructor properties", () => {
    expect(Function).toHaveLength(1);
    expect(Function.name).toBe("Function");
    expect(Function.prototype).toHaveLength(0);
    expect(Function.prototype.name).toBe("");
  });

  test("typeof", () => {
    expect(typeof Function()).toBe("function");
    expect(typeof new Function()).toBe("function");
  });

  test("basic functionality", () => {
    expect(Function()()).toBeUndefined();
    expect(new Function()()).toBeUndefined();
    expect(Function("return 42")()).toBe(42);
    expect(new Function("return 42")()).toBe(42);
    expect(new Function("foo", "return foo")(42)).toBe(42);
    expect(new Function("foo,bar", "return foo + bar")(1, 2)).toBe(3);
    expect(new Function("foo", "bar", "return foo + bar")(1, 2)).toBe(3);
    expect(new Function("foo", "bar,baz", "return foo + bar + baz")(1, 2, 3)).toBe(6);
    expect(new Function("foo", "bar", "baz", "return foo + bar + baz")(1, 2, 3)).toBe(6);
    expect(new Function("foo", "if (foo) { return 42; } else { return 'bar'; }")(true)).toBe(42);
    expect(new Function("foo", "if (foo) { return 42; } else { return 'bar'; }")(false)).toBe(
      "bar"
    );
    expect(new Function("return typeof Function()")()).toBe("function");
    expect(new Function("x", "return function (y) { return x + y };")(1)(2)).toBe(3);

    expect(new Function().name).toBe("anonymous");
    expect(new Function().toString()).toBe("function anonymous() {\n  ???\n}");
  });
});

describe("errors", () => {
  test("syntax error", () => {
    expect(() => {
      new Function("[");
    })
      // This might be confusing at first but keep in mind it's actually parsing
      // function anonymous() { [ }
      // This is in line with what other engines are reporting.
      .toThrowWithMessage(
        SyntaxError,
        "Unexpected token CurlyClose. Expected BracketClose (line: 1, column: 26)"
      );
  });
});