Glasgow | Sheetal kharab | Module Decomposition | Sprint 3| Middleware exercises

.gitignore

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+\node_modules

CustomMiddlewareVersion/customeMiddleware.js

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+import express from "express";
+
+const app = express();
+
+// Built-in middleware to parse JSON bodies
+app.use(express.json());
+
+//extract username from header
+const extractUsername = (req, res, next) => {
+  const usernameHeader = req.headers["x-username"];
+  req.username = usernameHeader ? usernameHeader : null;
+  next();
+};
+
+// validate JSON array from POST body
+const validateJsonArray = (req, res, next) => {
+  if (!Array.isArray(req.body)) {
+    return res.status(400).send("Expected a JSON array.");
+  }
+
+  const allStrings = req.body.every((item) => typeof item === "string");
+  if (!allStrings) {
+    return res.status(400).send("Array must contain only strings.");
+  }
+
+  next();
+};
+
+// Use the middlewares
+app.use(extractUsername);
+app.use(validateJsonArray);
+
+// Route handler
+app.post("/", (req, res) => {
+  const messages = [];
+
+  messages.push(
+    req.username
+      ? `You are authenticated as ${req.username}.`
+      : "You are not authenticated."
+  );
+
+  if (req.body.length > 0) {
+    messages.push(
+      `You have requested information about ${req.body.length} subject${
+        req.body.length > 1 ? "s" : ""
+      }: ${req.body.join(", ")}.`
+    );
+  } else {
+    messages.push("You have requested information about 0 subjects.");
+  }
+
+  res.send(messages.join("\n\n"));
+});
+
+// Start server
+app.listen(3000, () => {
+  console.log("Server running on port 3000");
+});

off-the-shelfMiddleware/builtIn.js

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+import express from "express";
+const app = express();
+
+const header = (req, res, next) => {
+  const userNameHeader = req.header["x-username"];
+  req.username = userNameHeader ? userNameHeader : null;
+  next();
+};
+app.use(header);
+app.use(express.json()); //built -in json parser
+
+app.post("/", (req, res) => {
+  const subjects = Array.isArray(req.body) ? req.body : [];
+
+  if (!subjects.every((item) => typeof item === "string")) {
+    return res.status(400).send("Expected an array of strings.");
+  }
+
+  const messages = [];
+  messages.push(
+    req.username
+      ? `You are authenticated as ${req.username}`
+      : "You are not authenticated."
+  );
+  messages.push(
+    subjects.length > 0
+      ? `You have requested information about ${
+          subjects.length
+        } subjects: ${subjects.join(", ")}`
+      : "You have requested information about 0 subjects."
+  );
+
+  res.send(messages.join("\n\n"));
+});
+
+app.listen(3001, () => {
+  console.log("Server running on port 3001 (built-in middleware version)");
+});