fs读取文件

es5

const fs = require('fs')
   fs.readFile(filename,'utf8',(err,data)=>{
      if(err) return reject(err)
      else{
       console.log(data)
      }
    })

es6写法1

const fs = require('fs')
const promisify= require('util').promisify
const readFile=promisify(fs.readFile)
async function test() {
  try {
      var data=await readFile(__dirname+'/process.js','utf8')
      console.log(data)
  } catch (e) {
    console.error(e)
  } finally {

  }
}
test()

es6写法2

const fs = require('fs')
const readFile=function (filename,args1) {
  return new Promise((resolve,reject)=>{
    fs.readFile(filename,args1,(err,data)=>{
      if(err) return reject(err)
      else{
        console.log("读文件")
        resolve(data)
      }
    })
  })
}
async function test() {
  try {
      var data=await readFile(__dirname+'/process.js','utf8')
      console.log(data)
  } catch (e) {
    console.error(e)
  } finally {

  }
}
test()