创建Person的一个实例,下面哪一个是正确的?
var Person john = new Person('John', 'Doe', 50, 'blue');
var john = new Person('John', 'Doe', 50, 'blue');
Person john = new Person('John', 'Doe', 50, 'blue');
new john = Person('John', 'Doe', 50, 'blue');