buitin middleware

Author: Faithy4444

middleware_exercise/builtin_middlewares/app.js

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+const express = require("express");
+const app = express();
+
+// Custom middleware: get username header
+function usernameMiddleware(req, res, next) {
+  const username = req.header("X-Username");
+  req.username = username ? username : null;
+  next();
+}
+
+// Built-in Express middleware to parse JSON
+app.post("/", usernameMiddleware, express.json(), (req, res) => {
+  const username = req.username;
+  const subjects = req.body;
+
+  if (!Array.isArray(subjects)) {
+    return res.status(400).send("Request body must be a JSON array.");
+  }
+  if (!subjects.every(item => typeof item === "string")) {
+    return res.status(400).send("All array elements must be strings.");
+  }
+
+  const count = subjects.length;
+  let response = "";
+  if (username) response += `You are authenticated as ${username}.\n\n`;
+  else response += "You are not authenticated.\n\n";
+
+  if (count === 1) response += `You have requested information about 1 subject: ${subjects[0]}.`;
+  else if (count > 1) response += `You have requested information about ${count} subjects: ${subjects.join(", ")}.`;
+  else response += "You have requested information about 0 subjects.";
+
+  res.send(response);
+});
+
+app.listen(3000, () => {
+  console.log("✅ Built-in middleware app running on http://localhost:3000");
+});

middleware_exercise/builtin_middlewares/package.json

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+{
+  "name": "builtin_middlewares",
+  "version": "1.0.0",
+  "main": "app.js",
+  "dependencies": {
+    "express": "^5.1.0"
+  }
+}