Implement express built in JSON middle and fix the request with curl.

Author: ike-agu

midlleware-Ex2/server.js

@@ -0,0 +1,41 @@
+const express = require("express");
+
+const app = express();
+app.use(express.json()); //built in JSON parser
+const PORT = 3000;
+
+function usernameMiddleware(req, res, next) {
+  const headerValue = req.header("X-Username"); // Express helper for headers
+  req.username = headerValue ? headerValue : null;
+  next();
+}
+
+app.post("/", usernameMiddleware,  (req, res) => {
+  // Validate: must be array of strings
+  if (
+    !Array.isArray(req.body) ||
+    !req.body.every((x) => typeof x === "string")
+  ) {
+    return res
+      .status(400)
+      .type("text")
+      .send("Invalid body. Expected a JSON array of strings.");
+  }
+
+  const username = req.username;
+  const authLine = username
+    ? `You are authenticated as ${username}.`
+    : `You are not authenticated.`;
+
+  const subjects = req.body; // should be an array of strings
+  const count = subjects.length;
+
+  let subjectsLine = `You have requested information about ${count} subject${count === 1 ? "" : "s"}`;
+  subjectsLine += count > 0 ? `: ${subjects.join(", ")}.` : `.`;
+
+  res.type("text").send(`${authLine}\n\n${subjectsLine}`);
+});
+
+app.listen(PORT, () => {
+  console.log(`Listening on http://localhost:${PORT}`);
+});