Add middleware: X-username header and JSON string-array body parser

- Add username middleware that reads X-username header and sets req.username (or null).
- Add array middleware that accumulates request bytes, parses JSON, validates it's an array of strings, assigns req.body or returns 400 on invalid input.
- Add package.json with Express dependency.

Author: Iswanna

middleware-exercise/app.js

@@ -0,0 +1,43 @@
+import express from "express";
+
+const usernameMiddleware = (req, res, next) => {
+  const headerValue = req.get("X-username");
+
+  if (headerValue) {
+    req.username = headerValue;
+  } else {
+    req.username = null;
+  }
+
+  next();
+};
+
+const arrayMiddleware = (req, res, next) => {
+  const bodyBytes = [];
+
+  // Every time a piece of data arrives, we put it in our list
+  req.on("data", (chunk) => {
+    bodyBytes.push(...chunk);
+  });
+
+  // When the whole message has arrived, we process it
+  req.on("end", () => {
+    const bodyString = String.fromCharCode(...bodyBytes);
+
+    const bodyObject = JSON.parse(bodyString);
+
+    if (
+      Array.isArray(bodyObject) &&
+      bodyObject.every((item) => typeof item === "string")
+    ) {
+      req.body = bodyObject;
+      next();
+    } else {
+      res
+        .status(400)
+        .send(
+          "Invalid request body. Expected a JSON array containing only strings.",
+        );
+    }
+  });
+};

middleware-exercise/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "middleware-exercise",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "express": "^5.2.1"
+  }
+}