在node.js中读写文件的三种方法总结

const { log } = require('console');
let fs = require('fs')
fs.readFile('./files/1.txt','utf8',function(err,dataStr){
	console.log(err);
	console.log('-------------');
	console.log(dataStr);
})

let niu = fs.readFileSync('./files/1.txt','utf8')
log("同步读取",niu)

//异步写入
fs.writeFile('./index1.txt',"开心阿松大",function(err){
	console.log(err);
	console.log('---------');
	console.log("写入成功");
})
//同步写入
let shangXin = fs.writeFileSync('./index2.txt',"伤心太平洋")

fs.open('./index1.txt','r',function(err,fd){    
	var buf = new Buffer(225);    //读取fd文件内容到buf缓存区
    fs.read(fd,buf,0,9,3,function(err,bytesRead,buffer){
        console.log(buf.slice(0,bytesRead).toString());
    }); 
    var buff = new Buffer(225);    //位置设置为null会默认从文件当前位置读取
    fs.read(fd,buff,0,3,null,function(err,bytesRead,buffer){
        console.log(buff.slice(0,bytesRead).toString());
    });    var buffer = new Buffer(225);    //同步方法读取文件
    var bytesRead = fs.readFileSync(fd,buffer,0,9,3);
    console.log(bytesRead);
    console.log(buffer.slice(0,bytesRead).toString());
});

var fs = require('fs');var buf = new Buffer('我喜爱编程');
fs.open('./mess.txt','w',function(err,fd){
    fs.write(fd,buf,3,9,0,function(err,written,buffer){
        fs.write(fd,buf,12,3,null,function(err,written,buffer){            if(err) console.log('写文件操作失败');
            console.log('写文件操作成功');
        });
    });    //同步写入
    fs.writeSync(fd,buf,3,9,0);
});

var fs = require('fs');var readStream = fs.createReadStream('./message.txt',{start:3,end:12});
readStream.on('open',function(fd){
    console.log('开始读取文件');
});
readStream.on('data',function(data){
    console.log('读取到数据：');
    console.log(data);
});
readStream.on('end',function(){
    console.log('文件已全部读取完毕');
});
readStream.on('close',function(){
    console.log('文件被关闭');
});
readStream.on('error',function(err){
    console.log('读取文件失败');
});

var fs = require('fs');var file = fs.createReadStream('./message.txt');var out = fs.createWriteStream('./anotherMessage.txt');
file.on('data',function(data){
    out.write(data);
});
out.on('open',function(fd){
    console.log('需要被写入的文件已打开');
});
file.on('end',function(){    //将操作系统缓存区中的数据全部写入文件
    out.end('再见',function(){
        console.log('文件全部写入完毕');
        console.log('共写入'+out.bytesWritten+'数据');
    });
});

//监听writeStream对象的drain事件var fs = require('fs');var out = fs.createWriteStream('./test1.txt');for(var i=0;i<10000;i++){    //返回true或false true代表缓存区已满
    var flag = out.write(i.toString());
    console.log(flag);
}
out.on('drain',function(){
    console.log('操作系统缓存区中的数据已全部输出');    var out = fs.createWriteStream('./test2.txt');    for(var i=0;i<10;i++){        var flag = out.write(i.toString());
        console.log(flag);
    }
    out.on('drain',function(){
        console.log('操作系统缓存区中的数据已全部输出');
    });
});

const fs = require('fs');
fs.readFile('./txt.txt','utf8',function(err,dataStr){
	if (err) {
		return console.log('读取失败'+err.message)
	}
	console.log('读取成功'+dataStr)
	let oldArr = dataStr.split(' ')
	console.log(oldArr)
	let arrNew = []
	oldArr.forEach(item=>{
		arrNew.push(item.replace('=',':'))
	})
	console.log(arrNew);
	// arrNew.join('\r\n')
	const  newArr = arrNew.join('\r\n')
	console.log(newArr);
	fs.writeFile('./txt1.txt',newArr,function(err){
		if (err) {
			console.log("写入失败"+err.message);
		}
		console.log("写入成功")
	})
})

fs.readFile(fpath.join(__dirname,'/files/1.txt'),'utf-8',function(err,dataStr){
	if (err) {
		console.log('file读取失败',err)
	} 
	console.log('file读取成功'+dataStr)
})