West Midlands | 26 March SDC | Iswat Bello | Sprint 3 | Middleware exercises#93
West Midlands | 26 March SDC | Iswat Bello | Sprint 3 | Middleware exercises#93Iswanna wants to merge 10 commits into
Conversation
- Exclude node_modules/ and package-lock.json from version control - Ignore environment variables (.env) and system files (.DS_Store) - Exclude build artifacts (dist/, build/) and log files (*.log) - Ignore VS Code workspace settings (.vscode/) - Reduce repository size and prevent committing sensitive data
- 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.
Enable ES module syntax (import/export) for the project by setting "type": "module" in package.json.
…dd route and start server - Create Express app instance and use PORT from process.env with 3000 fallback. - Add try/catch around JSON.parse in array middleware and return 400 on invalid JSON. - Add POST "/" route that composes response using usernameMiddleware and arrayMiddleware. - Start server with app.listen.
- Rename middleware-exercise/app.js to middleware-exercise/two custom-written middlewares.js - Clarifies that the file contains two custom middleware implementations
- Change condition in two-custom-written-middlewares.js from MessageCount <= 1 to MessageCount === 1 so "subject" is used only when there is exactly one item (zero now uses "subjects").
- Add off-the-shelf-middleware.js: create Express app and listen on PORT (env fallback to 3000). - Add username middleware (reads X-username header into req.username). - Add validateArray middleware (ensures JSON body is an array of strings; returns 400 on invalid input). - Add POST "/" route that composes a response using the middlewares and starts the server.
- Add README.md describing how to run the custom and off-the-shelf middleware demos. - Document key concepts: middleware pattern, manual parsing vs express.json, env PORT fallback, and process management. - Include curl examples for valid and invalid requests and note default port 3000.
Iswanna
added
📅 Sprint 3
nedssoft
added
Review in progress
nedssoft
left a comment
nedssoft
left a comment
There was a problem hiding this comment.
Really strong submission, Iswat — and thank you for the README especially. The "Key Concepts Learned" section and the curl examples made this a pleasure to review. 👏
A few things you've done really well:
- You validate that every item is a string, not just that the body is an array — lots of people stop at
Array.isArray, so well spotted. - In the custom parser you've wrapped
JSON.parsein atry/catch, so a malformed body returns a 400 instead of crashing the server. 👍 - You read
PORTfrom the environment with a sensible fallback.
I've left two questions to think about rather than fixes — nothing blocking the big picture. Have a look and let me know your thoughts!
| ) { | ||
| next(); | ||
| } else { | ||
| res.status(400).send("Error message"); |
There was a problem hiding this comment.
You wrote a really clear, helpful 400 message over in the custom version — "Invalid request body. Expected a JSON array containing only strings." Compare it with "Error message" here: which one helps the person calling your API understand what went wrong? Could this one tell them as much as the other does?
There was a problem hiding this comment.
The error message in the custom version is more descriptive because it explicitly tells the caller a JSON array of strings is required. This helps them identify exactly which part of their request was invalid, whereas 'Error message' leaves them guessing.
I have updated the error message accordingly.
There was a problem hiding this comment.
Perfect — and your explanation nails exactly why it matters: a descriptive error tells the caller what went wrong so they're not left guessing. 👍 It now matches your nice custom-version message. This is sorted — marking it Complete. (No need to chase the String.fromCharCode/Buffer question for this exercise — that was just an optional rabbit hole if it ever piques your curiosity.) Lovely work, Iswat.
|
|
||
| // When the whole message has arrived, we process it | ||
| req.on("end", () => { | ||
| const bodyString = String.fromCharCode(...bodyBytes); |
There was a problem hiding this comment.
Lovely manual parser! Since this exercise is all about handling raw bytes, try sending a value with an accent or an emoji — ["café"] or ["🐝"] — and see whether it comes back out intact.
Have a look at what String.fromCharCode does with the individual bytes of a multi-byte character, and whether Node gives you a tidier way to turn a set of byte chunks back into a string. (Something to investigate rather than copy: what could you do with the Buffer objects that data hands you?)
There was a problem hiding this comment.
String.fromCharCode will try to turn every single number into its own character. This distorted the output because special characters (like emojis or accents) are actually multi-byte, meaning they need 2 or 4 numbers to stay together to form one character. Buffer.concat keeps those numbers together so .toString() can read them correctly.
Kindly see two screenshots attached of when I used String.fromCharCode and Buffer.concat respectively
nedssoft
added
Reviewed
nedssoft
added
Complete
Thank you for the detailed feedback! I’m glad the README and the validation logic were clear. I’ve updated the code based on your questions. |
nedssoft
left a comment
nedssoft
left a comment
There was a problem hiding this comment.
Brilliant! I'm glad you went further to explore this and can appreciate the difference.
Good job 👍
|
Thank you! It was really eye-opening to see how the bytes were being 'shattered' in the console when I used the spread operator. I definitely have a much better understanding now of why Buffers are so important for handling real-world data like emojis and accents! |
2 participants
Learners, PR Template
Self checklist
Changelist
In this PR, I created two directories to demonstrate different approaches to Express middleware:
X-Usernameheader, and another (arrayMiddleware) manually handles raw data streams to parse and validate aJSONarray of strings.express.json()middleware. This version includes a streamlinedvalidateArraymiddleware to ensure the parsed body meets specific requirements.