在 Javascript 中，所有对象都继承自 Object.对于自定义对象，如果您没有定义 toString() 方法，它将从其父类继承它.因此 obj.toString() 打印[object Object]"，因为它是 Object 类型的对象(原始类型).

In Javascript all objects inherit from Object. For a custom object if you don't define the toString() method it will inherit it from its parent class. So obj.toString() prints "[object Object]" because it is an object (a primitive type) of type Object.