built-in middleware done

Author: RaihanSharif

built-in-middleware/app.js

@@ -0,0 +1,47 @@
+import express, { json } from "express";
+
+const app = express();
+app.use(express.json());
+app.use(express.urlencoded({ extended: true }));
+
+function usernameMiddleware(req, res, next) {
+    const username = req.get("X-username");
+    req.username = username;
+    console.log(username);
+    next();
+}
+
+app.use(usernameMiddleware);
+
+app.post("/", (req, res) => {
+    let responseStr = "";
+    if (req.username) {
+        responseStr = `You are authenticated as ${req.username}.\n`;
+    } else {
+        responseStr = `You are not authenticated.\n`;
+    }
+
+    if (req.body) {
+        console.log(req.body);
+        responseStr = responseStr.concat(
+            `You have requested information about ${req.body.length} subjects: ${req.body.join(", ")}.\n`,
+        );
+    }
+    res.send(responseStr);
+});
+
+/*
+previous CURL does not work because curl --data sends 'content-type: application/x-www-form-urlencoded', is not parsed by expres.json()
+but by urlencoded(), which tries to create a key:value pair set rather than an array. 
+
+By setting the content type explicitly, this can force the app to use the desired middleware:
+
+curl -X POST http://localhost:3000/ \
+  -H "Content-Type: application/json" \
+  -H "X-Username: Ahmed" \
+  --data '["Bees", "birds", "lizards"]'
+*/
+
+app.listen(3000, () => {
+    console.log(`Listening on port: 3000`);
+});