How to write elegant code?(Part 2)

I have talked about the basic principles。And in this section I am diving into the details， take asynchronous actions and exception as example。 Enjoy yourself~~

一 asynchronous actions

  we have to deal with the time cuppling whenever we writing asynchronous ations. make ajax calls, read files etc.  someone writes code inside the callback function， its fine when you'r in charge of small application ， but as the app growsup，it may confuse youself very much， especially for the one who take over your work。 and。。。。 quiet  terrible。

(todo)

二 Exception handling

   (todo)