const fs = require('fs')

function getFileByPath(fpath) {
  return new Promise(function (resolve, reject) {
    fs.readFile(fpath, 'utf-8', (err, dataStr) => {
      if (err) return reject(err)
      resolve(dataStr)
    })
  })
}

getFileByPath('./files/1.txt')
  .then(function (data) {
    console.log(data)
    return getFileByPath('./files/22.txt')
  })
  .then(function (data) {
    console.log(data)
    return getFileByPath('./files/3.txt')
  })
  .then(function (data) {
    console.log(data)
  })
  .catch(function (err) {     
    console.log('这是自己的处理方式：' + err.message)
  })

//或者 读写文件 promise
const fs = require('fs')
let readFile = function(path){
    return new Promise(resolve => {
        fs.readFile(path,  (error, data) => {
            resolve(data)
          })
    })
  }
  
let writeFile = function(path, data){
    return new Promise(resolve => {
        fs.writeFile(path, data, error => { 
            if (error) {
                console.log('写入失败')
              } else {
                resolve(data)
                console.log('写入成功了')
              }
          })
    })
  }