Replace custom JSON parser with express.json built-in middleware

Author: Fatma Degirmenci

express-middleware-exercise/server2.js

@@ -0,0 +1,54 @@
+const express = require("express");
+const app = express();
+
+const PORT = 3000;
+
+app.use(express.json());
+
+app.listen(PORT, () => {
+  console.log(`server running on http://localhost:${PORT} `);
+});
+
+
+function usernameMiddleware(req, res, next) {
+  const username = req.get("X-Username");
+  req.username = username || null;
+  next();
+}
+function bodyMiddleware(req, res, next) {
+  const body = req.body;
+  if (!Array.isArray(body) || !body.every((el) => typeof el === "string")) {
+    return res.status(400).send("Body must be an array of strings");
+  }
+  next();
+}
+app.post("/subjects", usernameMiddleware, bodyMiddleware, (req, res) => {
+  const username = req.username;
+  const subjects = req.body;
+
+  let authMessage;
+
+  if (username) {
+    authMessage = `You are authenticated as ${username}`;
+  } else {
+    authMessage = `You are not authenticated.`;
+  }
+  let countSubject = subjects.length;
+
+  let subjectsText;
+  if (countSubject === 1) {
+    subjectsText = "subject";
+  } else {
+    subjectsText = "subjects";
+  }
+
+  let subjectList;
+  if (countSubject > 0) {
+    subjectList = `: ${subjects.join(", ")}`;
+  } else {
+    subjectList = "";
+  }
+  res.send(
+    `${authMessage}\n\nYou have requested information about ${countSubject} ${subjectsText}${subjectList}.`
+  );
+});