昨天看了这个 bluebird 多层嵌套该如何优化。 地址 然后前天正好自己学习promise得时候先这么写了

checkMeetingPath = (meetingPath)->
   console.log('s1')
   return fs.existsAsync(meetingPath)
   .then (exists)->
      console.log('s2')
      return fs.mkdirAsync(meetingPath)
   .catch (exists)->
      console.log('s8')
      return fs.statAsync(meetingPath)
       .then (stats)->
           console.log('s5')
           if stats.isDirectory()
             console.log('s6')
             return Promise.resolve() 
           else
             console.log('s7')
             return fs.unlinkAsync(meetingPath)
             .then ()->
               console.log('s3')
               return fs.mkdirAsync(meetingPath)

昨天看了那个之后做了一点优化 如下：

checkMeetingPath = (meetingPath)->
  notExists = (exists)->
    console.log('s2')
    return fs.mkdirAsync(meetingPath)
  isExists = (exists)->
    console.log('s8')
    return fs.statAsync(meetingPath)
    .then isDirectory
  isDirectory = (stats)->
    console.log('s5')
    if stats.isDirectory()
      console.log('s6')
      return Promise.resolve() 
      # return Promise.reject('dd') 
    else
      console.log('s7')
      return fs.unlinkAsync(meetingPath)
      .then notExists
    
  console.log('s1')
  return fs.existsAsync(meetingPath)
  .then notExists
  .catch isExists

感觉这样优化之后已经舒服了很多了。。不知道哪里可以更加舒服一点， 比如每个return得promise我加得这个then如何更加优雅什么得。