node罕用内置模块(fs模块)
划分：
文件操作的三个基本概念：权限位、标识符、操作符
1.基本操作类
2.罕用API
个别分为异步操作与同步操作，这里应用异步操作试验(一次性的文件操作，没有应用buffer)，Node.js中有谬误优先的概念，当操作可能会呈现谬误时，回调函数的第一个参数常是谬误对象
const fs = require('fs');const path = require('path');// readFilefs.readFile(path.resolve('msg.txt'), 'utf-8', (error, data) => { if (!error) console.log(data);});// writeFile (overwrite)，门路不存在时，会创立门路，操作配置对象，可省略fs.writeFile(path.resolve('msg.txt'), 'Hello Node.js', { mode: 0o666, // 权限 flag: 'a+', // 追加 encoding: 'utf-8' // 编码}, (error) => { if (!error) console.log('write success');})// apendFilefs.appendFile(path.resolve('msg.txt'), '\nHello Node.js', {}, (err) => { if (!err) console.log('append success');});// copyFilefs.copyFile(path.resolve('msg.txt'), path.resolve('msg2.txt'), (err) => { if (!err) console.log('copy success');});// watchFilefs.watchFile(path.resolve('msg.txt'), { interval: 1000},(curr, prev) => { console.log(curr.mtime); console.log(`${curr.size} ${prev.size}`);})fs.appendFile(path.resolve('msg.txt'), '\nHello Node.js', {}, (err) => { if (!err) console.log('append success22'); setTimeout(() => { fs.unwatchFile(path.resolve('msg.txt')); // 勾销监听 }, 2000);});open and close：
fs.open(path.join(__dirname,'msg.txt'),'r',(error,fd)=>{ if(!error){ console.log(fd); fs.close(fd,(err)=>{ if(!err) console.log('close success'); }); }});// 文件读写：
const fs = require('fs');const path = require('path');/** * read 将数据从磁盘文件中读取到内存中的buffer * fd 定位以后被关上的文件 * buffer 存储读取到的数据 * offset 示意在buffer那个地位上写入 * length 读入buffer的长度 * position 从磁盘文件中的那个地位开始读取 */let buf = Buffer.alloc(10);fs.open(path.join(__dirname,'msg.txt'),'r',(err,rfd)=>{ if(err) throw err; fs.read(rfd,buf,1,4,2,(err,readBytes,buffer)=>{ console.log(readBytes); console.log(buffer); console.log(buffer.toString()); }) fs.close(rfd);})/** * write 将数据从内存中buffer的数据写入到磁盘文件中 */let buf2 = Buffer.from('1234567890');fs.open('b.txt','w',(err,wfd)=>{ fs.write(wfd,buf2,1,4,0,(err,written,buffer)=>{ console.log(written); console.log(buffer); console.log(buffer.toString()); }) fs.close(wfd);})封装文件copy：
const fs = require('fs');const path = require('path');function fileCopy(resFile, newFile, bufLen) { let buf = Buffer.alloc(bufLen); let readOffset = 0; fs.open(resFile, 'r', (err, rfd) => { if (err) throw err; fs.open(newFile, 'w', (err, wfd) => { if (err) throw err; function readAnWrite() { fs.read(rfd, buf, 0, bufLen, readOffset, (err, readBytes, buffer) => { if (!readBytes) { // readBytes === 0 阐明读取结束 fs.close(rfd, () => { }); fs.close(wfd, () => { }); console.log('copy success'); return; } readOffset += readBytes; fs.write(wfd, buf, 0, readBytes, err => { if (err) throw err; readAnWrite(); }); }); } readAnWrite(); }) })}fileCopy(path.join(__dirname, 'msg.txt'), path.join(__dirname, 'b.txt'), 5);3.常见操作目录API
api:
const fs = require('fs');const path = require('path');// access 判断是否有权限拜访文件或目录fs.access(path.join(__dirname,'b.txt'),err=>console.log(err?err:'success'));// stat 获取文件信息fs.stat(path.join(__dirname,'b.txt'),(err,stats)=>{ if(!err) console.log(stats.isFile());});// mkdir 创立目录fs.mkdir(path.join(__dirname,'test/jiang'),{recursive:true},err=>console.log(err?err:'make success'));// rmdir 删除目录fs.rmdir(path.join(__dirname,'test'),{recursive:true},err=>console.log(err?err:'dir remove success'));// readdir 读取目录 返回文件名、目录数组fs.readdir(path.join(__dirname,'./'),(err,files)=>{ if(!err) console.log(files);});// unlink 删除文件fs.unlink(path.join(__dirname,'b.txt'),err=>console.log(err?err:'file remove success'));目录创立之同步实现：
const fs = require('fs');const path = require('path');// access 判断是否有权限拜访文件或目录fs.access(path.join(__dirname,'b.txt'),err=>console.log(err?err:'success'));// stat 获取文件信息fs.stat(path.join(__dirname,'b.txt'),(err,stats)=>{ if(!err) console.log(stats.isFile());});// mkdir 创立目录fs.mkdir(path.join(__dirname,'test/jiang'),{recursive:true},err=>console.log(err?err:'make success'));// rmdir 删除目录fs.rmdir(path.join(__dirname,'test'),{recursive:true},err=>console.log(err?err:'dir remove success'));// readdir 读取目录 返回文件名、目录数组fs.readdir(path.join(__dirname,'./'),(err,files)=>{ if(!err) console.log(files);});// unlink 删除文件fs.unlink(path.join(__dirname,'b.txt'),err=>console.log(err?err:'file remove success'));目录创立之异步实现：
const fs = require('fs');const path = require('path');const {promisify} = require('util');// 回调函数模式function mkDir(dirPath, cb) { let parts = dirPath.split('/'); let index = 1; function next() { if (index > parts.length) return cb && cb(); let current = parts.slice(0,index++).join('/'); fs.access(current,(err)=>{ if(err){ fs.mkdir(current,next); // 创立目录，用回调函数创立下一层目录 }else{ next(); } }) } next();}mkDir('test/test2/test3', () => { console.log('创立胜利')})// 将access 与 mkdir 解决成async/await 格调// promise 模式const access = promisify(fs.access);const mkdir = promisify(fs.mkdir);async function myMkDir(dirPath,cb){ let parts = dirPath.split('/'); for(let index = 1; index <= parts.length;index++){ let current = parts.slice(0,index).join('/'); try{ await access(current); }catch(err){ await mkdir(current); } } cb && cb();}myMkDir('test/test2/test3',()=>{ console.log('创立胜利')});目录删除之异步：
function myRemDir(dirPath, cb) { fs.stat(dirPath, (err, stats) => { if (stats.isDirectory()) { // 目录 fs.readdir(dirPath, (err, files) => { let dirs = files.map((item) => path.join(dirPath, item)); let index = 0; function next() { if (index == dirs.length) { return fs.rmdir(dirPath, cb); } else { myRemDir(dirs[index++], next); } } next(); }) } else { fs.unlink(dirPath, cb); } });}myRemDir(path.join(__dirname, 'temp'), () => { console.log('删除胜利');})