Javascript --- problems related to this (solving this) (updating continuously ...)

1. Use this in the prototype

<! Doctype html> 

Error analysis:

A: this actually refers to the window object, not the current instance object.

Count () and count in B: And C: actually refer to a separate function named count (), but it can also be window. count (), because window. count () can be omitted as count ()


D: Direct the variable self to the current instance object, so that the js parsing engine will not confuse who this refers.
In addition, when setTimeout () is passed in this, of course it refers to the current Object window to which it belongs (because setTimeout () is a window method !!!)