以流的方式读取与写入文件

读取

 const fs = require('fs');
 var readStream=fs.createReadStream('./nodespace/module/1.txt');
 var count=0;
 var str=''
 readStream.on('data',(data)=>{
     str+=data;
     count++;
​
 })
 readStream.on('end',()=>{
   console.log(str)
   console.log(count)
​
})
readStream.on('error',(err)=>{
    console.log(err)
})
​

写入

const fs = require('fs');
var str='';
for(var i=0;i<500;i++){
    str+='保存数据
';//写入500次
}
var writeStream=fs.createWriteStream('./nodespace/module/1.txt');
writeStream.write(str)
//写入完成
writeStream.end();
writeStream.on('finish',()=>{
    console.log("写入完成");
    
})

管道流（适合大文件）(把一个文件复制到另一个文件夹里)

const fs = require('fs');
var readStream=fs.createReadStream('./1111.jpg')
var writeStream=fs.createWriteStream('./nodespace/module/2222.jpg');
readStream.pipe(writeStream)