[Octane]

function F(x) {
	if (this.constructor == F) {
		this.x = x;
	}
	return this.x;
}

var f = new F(3), obj = {x: 5};

alert(f.x); //3

alert(F.call(obj)); //5
*!*
alert(F.call(f)); //ожидаем получить 3, а будет undefined
*/!*