}

func node() (version string, ok bool) {
	// Try the https://nodejs.org/api/process.html#processversion API.
	p := js.Global().Get("process")
	if p.IsUndefined() {
		return "", false
	}
	v := p.Get("version")
	if v.IsUndefined() {
		return "", false
	}
	return v.String(), true

		errMsg := err.Call("toString").String()
		// Errors can optionally contain a cause.
		if cause := err.Get("cause"); !cause.IsUndefined() {
			// The exact type of the cause is not defined,
			// but if it's another error, we can call toString() on it too.
			if !cause.Get("toString").IsUndefined() {
				errMsg += ": " + cause.Call("toString").String()
			} else if cause.Type() == js.TypeString {
				errMsg += ": " + cause.String()

		t.Errorf("NaN is equal to NaN")
	}
}

func TestUndefined(t *testing.T) {
	if !js.Undefined().IsUndefined() {
		t.Errorf("undefined is not undefined")
	}
	if !js.Undefined().Equal(js.Undefined()) {
		t.Errorf("undefined is not equal to undefined")
	}
	if dummys.IsUndefined() {
		t.Errorf("object is undefined")
	}
	if js.Undefined().IsNull() {
		t.Errorf("undefined is null")
	}

	return v.ref == w.ref && v.ref != valueNaN.ref
}

// Undefined returns the JavaScript value "undefined".
func Undefined() Value {
	return valueUndefined
}

// IsUndefined reports whether v is the JavaScript value "undefined".
func (v Value) IsUndefined() bool {
	return v.ref == valueUndefined.ref
}

// Null returns the JavaScript value "null".
func Null() Value {
	return valueNull
}

	_, err := fsCall("fchown", fd, uint32(uid), uint32(gid))
	return err
}

func Lchown(path string, uid, gid int) error {
	if err := checkPath(path); err != nil {
		return err
	}
	if jsFS.Get("lchown").IsUndefined() {
		// fs.lchown is unavailable on Linux until Node.js 10.6.0
		// TODO(neelance): remove when we require at least this Node.js version
		return ENOSYS
	}
	_, err := fsCall("lchown", path, uint32(uid), uint32(gid))