Refactor jsonArrayMiddleware into reusable middlewares for parsing and validation

Author: Mikiyas-STP

middleware_exercise/custom_middleware/expressmiddlewareapp.js

@@ -2,77 +2,76 @@
 const express = require("express");
 const app = express();
 //my first middleware , request/get the header and attach it to req
-
 function userNameMiddleware(req, res, next) {
-    const username = req.header("X-Username");  
-    req.username = username ? username : null;
-    next(); //to pass control onward
+  const username = req.header("X-Username");  
+  req.username = username ? username : null;
+  next(); //to pass control onward
 }
-
-//my second middleware json array middleware.. manually parsing raw body into json
-function jsonArrayMiddleware(req, res, next) {
-    let data = '';
-    
-    //collecting the chunk of data as soon as they arrive
-    req.on("data", chunk => {
-        data += chunk;
-    });
-    
-    req.on("end", () => {
-      try {
-        const parsed = JSON.parse(data);
-
-        //checking if it is an array
-        if (!Array.isArray(parsed)) {
-          return res.status(400).send("Request body must be a JSON array.");
-        }
-        // check every item is a string
-        const allStrings = parsed.every((item) => typeof item === "string");
-        if (!allStrings) {
-          return res.status(400).send("All array elements must be strings.");
-        }
-
-        req.body = parsed;
-        next();
-      } catch (err) {
-        res.status(400).send("Invalid JSON.");
-      }
-    });
+// middleware 1: parse raw JSON into req.body
+function parseJsonMiddleware(req, res, next) {
+  let data = '';
+  // collecting the chunk of data as soon as they arrive
+  req.on("data", chunk => {
+    data += chunk;
+  });
+  req.on("end", () => {
+    try {
+      req.body = JSON.parse(data); // parse JSON only, no checks yet
+      next();
+    } catch (err) {
+      res.status(400).send("Invalid JSON.");
+    }
+  });
 }
+// middleware 2 check if req.body is an array
+function validateArrayMiddleware(req, res, next) {
+  if (!Array.isArray(req.body)) {
+    return res.status(400).send("Request body must be a JSON array.");
+  }
+  next();
+}
+// middleware 3: check if every item in the array is a string
+function validateStringArrayMiddleware(req, res, next) {
+  const allStrings = req.body.every((item) => typeof item === "string");
+  if (!allStrings) {
+    return res.status(400).send("All array elements must be strings.");
+  }
+  next();
+}
+// my route handler
+app.post(
+  "/",
+  userNameMiddleware,
+  parseJsonMiddleware,
+  validateArrayMiddleware,
+  validateStringArrayMiddleware,
+  (req, res) => {
+    const username = req.username;
+    const subjects = req.body;
+    const count = subjects.length;
 
-//my route handler
-app.post("/", userNameMiddleware, jsonArrayMiddleware, (req, res) => {
-  const username = req.username;
-  const subjects = req.body;
-  const count = subjects.length;
-
-  let response = "";
+    let response = "";
 
-  // Auth message
-  if (username) {
-    response += `You are authenticated as ${username}.\n\n`;
-  } else {
-    response += "You are not authenticated.\n\n";
-  }
+    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.";
+    }
 
-  // Subject count message
-  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);
   }
+);
 
-  res.send(response);
-});
-
-//start the server
 app.listen(3000, () => {
   console.log("Server running on http://localhost:3000");
 });
 
-//to run node app.js
-//on other terminal  curl -X POST --data '["Bees"]' -H "X-Username: Ahmed" http://localhost:3000
+// to run: node app.js
+// on another terminal: curl -X POST --data '["Bees"]' -H "X-Username: Ahmed" http://localhost:3000