JavaScript class and Inheritance of this attribute usage instructions _ js object-oriented

This article describes the this attribute in JavaScript. This attribute is an important basis for understanding JavaScript classes and inheritance. This attribute indicates the current object. If this is used in the global scope, it indicates the current page Object window. If this is used in the function, this indicates what is called Based on the object on which the function is called at runtime. We can also use the apply and call global methods to change the specific point of this in the function.
First, let's look at an example of using this in the global scope:

The Code is as follows: