[mabel] Edit error handling, joi, routers for express.js

Author: mabelleeyanhwa

docs/backend-web-development/express-error-handling.md

@@ -40,7 +40,7 @@ Within an error handler, you typically need to do one of two things:
 - call `next(err)` to pass the execution to the next error handler
 
 ```js
-app.use(function (err, req, res, next) {
+app.use((err, req, res, next) => {
   res.status(500);
   res.send(
     `Error: ${err} </br>
@@ -59,19 +59,19 @@ We can define properties to the error object such as a `code` so that we can ret
 app.get("/", (req, res) => {
   // synchronous error
   error = new Error(" 😱! Error! Error!");
-  error.code = 200;
+  error.statusCode = 200;
   throw error;
 });
 ```
 
-Return the correct status code in the response header if `err.code` is defined. Else we will default to the error code `500`.
+Return the correct status code in the response header if `err.statusCode` is defined. Else we will default to the error code `500`.
 
 ```js
-app.use(function (err, req, res, next) {
-  res.status(err.code || 500);
+app.use((err, req, res, next) => {
+  res.status(err.statusCode || 500);
   res.send(
     `Error: ${err} </br>
-    Error Status Code: ${err.code} <br>
+    Error Status Code: ${err.statusCode} <br>
     Error stack: ${err.stack}`
   );
 });
@@ -84,7 +84,7 @@ Refer to the script: [Express.js playground: error_handler_example_3](https://gi
 If you call an asynchronous API in a route handler and you would like to handle errors returned/thrown by those asynchronous operations, you just need to call `next(err)` when some error happens. That is, you call the `next` callback (which is an argument of every middleware and route handler) with an instance of _Error_.
 
 ```js
-app.get("/", function (req, res, next) {
+app.get("/", (req, res, next) => {
   // assume some asynchronous error happens because of an network issue
   const err = new Error("Unexpected network error");
   next(err);
@@ -94,15 +94,15 @@ app.get("/", function (req, res, next) {
 Let's add a route handler that will not be called because it will be skipped when the error is thrown.
 
 ```js
-app.get("/", function (req, res, next) {
+app.get("/", (req, res, next) => {
   console.log("You should not see this line in the console 😡");
 });
 ```
 
 Add a custom error handler that will catch the error and then pass it on to the next error handler.
 
 ```js
-app.use(function (err, req, res, next) {
+app.use((err, req, res, next) => {
   if (err.message === "Unexpected network error") {
     console.log("I don't know how to handle network error. Pass it on.");
     next(err);
@@ -116,9 +116,9 @@ app.use(function (err, req, res, next) {
 Add a final custom error handler that will return a response to the client.
 
 ```js
-app.use(function (err, req, res, next) {
-  res.status(500);
-  res.send({ error: "internal server error" });
+app.use((err, req, res, next) => {
+  err.statusCode = err.statusCode || 500;
+  res.status(err.statusCode).send(err.message);
 });
 ```
 

docs/backend-web-development/express-joi-validation.md

@@ -84,10 +84,7 @@ const schema = Joi.object({
   password: Joi.string().pattern(new RegExp("^[a-zA-Z0-9]{3,30}$")),
   repeat_password: Joi.ref("password"), // must equal to password
 
-  birthyear: Joi.number()
-    .integer()
-    .min(1900)
-    .max(2013), // an integer between 1900 and 2013
+  birthyear: Joi.number().integer().min(1900).max(2013), // an integer between 1900 and 2013
 
   //email a valid email address string
   //must have two domain parts e.g. example.com
@@ -132,12 +129,8 @@ We could put the schema in a function that will return the result object.
 function validateSong(song) {
   const schema = Joi.object({
     id: Joi.number().integer(),
-    name: Joi.string()
-      .min(3)
-      .required(),
-    artist: Joi.string()
-      .min(3)
-      .required(),
+    name: Joi.string().min(3).required(),
+    artist: Joi.string().min(3).required(),
   });
   return schema.validate(song);
 }
@@ -151,6 +144,6 @@ if (validation.error) {
   const error = new Error(validation.error.details[0].message);
   // 400 Bad Request
   error.statusCode = 400;
-  return next(error);
+  next(error);
 }
 ```

docs/backend-web-development/express-lab.md

@@ -139,10 +139,6 @@ Implement tests with Jest and Supertest (include testing for errors)
 
 Integrate Express.js routers to organise your "who is next" routes (put into routes folder)
 
-## Refactoring to controllers folder
-
-Lab: refactoring of routes
-
 ## Error
 
 Integrate a default error handler middleware for your "who is next" routes
@@ -156,6 +152,5 @@ Integrate Joi validation library to validate data
 - package.json
 - package-lock.json
 - src
-  - controllers
   - routes
 - \_\_tests\_\_

docs/backend-web-development/express-routers.md

@@ -198,6 +198,12 @@ Now we can support both API versions!
 What do you see when you go to http://localhost:3000/v1 on the browser?
 How about http://localhost:3000/v2 ?
 
+## How to really solve the versioning problem?
+
+Should we stick to versioning like what we do in REST or change to an evolution style where we still try to support old endpoints as much as possible? There is no easy answer.
+
+https://github.com/graphql/graphql-spec/issues/134
+
 ## Exercises
 
 Now that we have both movies and songs routes on the same App.js file, we should split them into a movies router and songs router.