// 數據存儲在users.json文件中const express = require("express");const fs = require("fs");const cors = require("cors");const bodyParser = require("body-parser");const app = express();app.use(cors({ origin: "*" })); // fix 跨域app.use(bodyParser.json()); // for parsing application/jsonapp.use(bodyParser.urlencoded({ extended: true })); // for parsing application/x-www-form-urlencoded// 新增app.post("/addUser", (req, res) => { fs.readFile("./users.json", "utf8", (err, data) => {  if (err) {   throw err;  }  data = data ? JSON.parse(data) : [];  data.push(req.body);  fs.writeFile("./users.json", JSON.stringify(data), err => {   if (err) throw err;   res.end();  }); });});// 刪除app.delete("/delUser/:id", (req, res) => { const id = req.params.id; fs.readFile("./users.json", "utf8", (err, data) => {  data = JSON.parse(data) || [];  const saveData = data.filter(item => item.id != id);  fs.writeFile("./users.json", JSON.stringify(saveData), err => {   if (err) throw err;   res.end();  }); });});// 修改app.put("/update/:id", (req, res) => { const id = req.params.id; const body = req.body; fs.readFile(__dirname + "/" + "users.json", "utf8", (err, data) => {  const userList = (data && JSON.parse(data)) || [];  const index = userList.findIndex(item => item.id == id);  userList[index] = { ...userList[index], ...body };  fs.writeFile("./users.json", JSON.stringify(userList), err => {   if (err) throw err;   console.log("修改");   res.end();  }); });});// 列表查詢app.get("/listUsers", function(req, res) {  fs.readFile(__dirname + "/" + "users.json", "utf8", function(err, data) {   console.log(data);   res.end(data);  });});app.listen(8081, function() { console.log("訪問地址: http://localhost:8081");});