let http = require('http');
http.createServer((req,res)=>{
   res.end();
}).listen(3000,()=>{
  console.log('start');
})

let fs = require('fs');
let readStream = fs.createReadStream('./nodedemo/1.txt');
let writeStream =fs.createWriteStream('./nodedemo/2.txt','utf-8');
readStream.pipe(writeStream);//读写流操作
//
let str = '';
readStream.on('data',(chunk)=>{
  str+=chunk;//chunk是 片段 //data是数据 不能修改。
});
readStream.on('end',(chunk)=>{
  console.log(str);//监听读写是否结束。
})