const Koa = require('koa');const path = require('path');const fs = require('fs');let mimes = {  'css': 'text/css',  'html': 'text/html',  'jpg': 'image/jpeg',  'jpeg': 'image/jpeg',  'json': 'application/json',  'js': 'text/javascript',  'xml': 'text/xml',  'png': 'image/png',  'pdf': 'application/pdf',  'less': 'text/css',  'gif': 'image/gif',  'txt': 'text/plain',  'tiff': 'image/tiff',  'svg': 'image/svg+xml'};// Scan dirfunction walk(reqPath) {  let files = fs.readdirSync(reqPath);  let fileList = [];  for (let i = 0, len = files.length; i< len; i++) {    let item = files[i];    if (item.startsWith('.')) {      continue;    }    let realPath = reqPath + '/' + files[i];    if (isDir(realPath)) {      fileList.push(filter(reqPath, files[i]));    } else {      fileList.push(files[i]);    }  }  return fileList;}function isDir(path){   return fs.existsSync(path) && fs.statSync(path).isDirectory(); } //function filter(reqPath, filePath) {  let files = fs.readdirSync(reqPath + '/' + filePath);  for (let i = 0; i < files.length; i++) {    let item = files[i];    if (item.endsWith('index.html')) {      return filePath + '/' + 'index.html';    }  }  return filePath;}function dir(url, reqPath) {  let contentList = walk(reqPath);  let result = '<div align="center" style="font-family:arial;font-size:30px;">Product Document</div><ul>';  if (url == '/') {    url = '';  }  for (let [index, item] of contentList.entries()) {    let realHref = url + '/' + item;    let realItem = item.split('/');    result += '<li> <a style="font-family:arial;font-size:20px;" href=' + realHref + '>' + realItem[0] + '</a></li>';  }  result = result + '</ul>';  return result;}async function file (url, filePath) {  let resultMime = parseMime(url);  let content;  if (resultMime && resultMime.indexOf('image/') >= 0) {    content = fs.readFileSync(filePath, 'binary');  } else {    content = fs.readFileSync(filePath, 'utf8');  }  return content;}async function content(ctx, fullStaticPath) {  let url = decodeURI(ctx.url);  let reqPath = path.join(fullStaticPath, url);  let exist = fs.existsSync(reqPath);  let content = '';  if (!exist) {    content = 'Local file not exists';  } else {    let stat = fs.statSync(reqPath);    if (stat.isDirectory()) {      content = dir(ctx.url, reqPath);    } else {      content = await file(ctx.url, reqPath);    }  }  return content;}function parseMime(url) {  let extName = path.extname(url);  extName = extName ? extName.slice(1) : 'unknown';  return mimes[extName];}const app = new Koa();const staticPath = '../onlinedoc';`請輸入代碼`app.use(async(ctx) => {  let fullStaticPath = path.join(__dirname, staticPath);  let resultContent = await content(ctx, fullStaticPath);  let resultMime = parseMime(ctx.url);  if (resultMime) {    ctx.type = resultMime;  }   if(resultMime && resultMime.indexOf('image/') >= 0) {    ctx.res.writeHead(200);    ctx.res.write(resultContent, 'binary');    ctx.res.end();  } else {    ctx.body = resultContent;  }});app.listen(8080, () => {  console.log('Running');});