WEB322 Assignment 2 Solution

Create and publish a web app that uses multiple routes which serve static files (HTML & CSS) as well as create a "data service" module for accessing data. This will serve as the "scaffolding" for future assignments.
Specification:
This assignment will involve creating multiple routes that serve specific HTML pages & JSON.
Part 1: Dev Environment, Home & About

Step 1: Development Environment
• Create a folder called web322-app. This will serve as our main application that we will be updating and modifying throughout this course.
• Inside this folder, initialize a local Git repository (using git init from the integrated terminal)
• Add the file server.js
• Add the file data-service.js
• Create a package.json file using npm init. Ensure that your "entry point" is server.js (this should be the default), and "author" is your full name, ie: "John Smith"
• Obtain the Express.js module using npm install express --save
• Commit your changes to your local git repository (using the source control icon showing the number of changes) with the message "initial commit"

Step 2: Adding Files / Folders
• Add the folder views - this will be the location of the .html files that we will be using in our application
• Add the folder public - this will be the location of the .css, client side .js & image files that we use in our application
• Add the folder data - this will be a temporary source of static data (JSON) for our application
• Inside the views folder, add the files home.html and about.html
• Inside the public folder, add the folder css
• Inside the public/css folder - add the file site.css (this will serve as the main .css file for our app)
• Your folder structure should now look like the image to the right:

Step 3: Adding Static Content (home.html & about.html)
• At this point, both files should be exactly the same, however we must make some changes to each page (what's currently there is only a starting point) o home.html
▪ Update "Link 1" to read "Home"
▪ Update "Link 2" to read "About" and change it's "href" property from "#" to "/about":
▪ Update the page "title" to read "Home"
▪ Ensure the heading (h2) for the left column reads "Coming Soon" - and provide a relevant message to the user
▪ Ensure the heading (h2) for the right column reads "Welcome" o about.html
▪ Update "Link 1" to read "Home", remove the class "active" from the parent <li> element and change the link's "href" property from "#" to "/home
▪ Update "Link 2" to read "About" and add the class "active" to the parent <li> element
▪ Update the page "title" & heading (h2) to read "About"
▪ Modify the grid layout from 2 columns to 1 (col-md-12) column. This was discussed in WEB222, but you can reference week 11 ("Responsive Grid System" -
http://zenit.senecac.on.ca/~patrick.crawford/index.php/web322/course-notes/week11-class1/ if you need further help
o (both home.html & about.html)
▪ modify the "navbar-brand" span element to read "WEB322 - Student Name" where "Student Name" is your name, ie "John Smith", etc
▪ Update "Link 3" to read "Employees" and change it's "href property from "#" to "/employees"
▪ Update "Link 4" to read "Managers" and change it's "href property from "#" to "/managers" ▪ Update "Link 5" to read "Departments" and change it's "href property from "#" to "/departments"

Step 4: Update server.js & testing the app
• Now that all the files are in place, update your server.js file according to the following specifications (HINT: Refer to the sample code from week 2 for reference):
o The server must make use of the "express" module o The server must listen on process.env.PORT || 8080
o The server must output: "Express http server listening on port" - to the console, where port is the port the server is currently listening on (ie: 8080)
o The route "/" must return the home.html file from the views folder o The route "/about" must return the about.html file from the views folder
o NOTE: for your server to correctly return the "css/site.css" file, the "static" middleware must be used: in your server.js file, add the line: app.use(express.static('public')); before your "routes" - we will discuss this in greater detail in Week 4
o From the integrated terminal, enter the command node server.js and verify the following: ▪ The integrated terminal shows "Express http server listening on 8080" ▪ The url: http://localhost:8080 shows the "Home" page:



▪ The url: http://localhost:8080/about shows the "About" page


Part 2: Data Service, Employees, Managers & Departments

Step 1: Obtaining the Data
• Create 2 new files inside the "data" folder: departments.json and employees.json
• Open your web browser and navigate to: this link (departments.json) and copy the contents of the JSON file to your own departments.json file (within the "data" folder).
• Next, navigate to: this link (employees.json) and copy the entire contents of the JSON file to your own employees.json file (within the "data" folder) - this should be an array of 280 "employee" objects
Step 2: Updating the custom data-service.js module
• The file that we added at the beginning of this assignment ("data-service.js") is going to be a module that we will use within our server.js file.
• Your first step is to "require" this module at the top of your server.js file so that we can use it to interact with the data from server.js

Step 3: Adding additional Routes:

We will be making use of this employee data from a different location from our "/" and "/about" routes. These routes will serve as the public-facing pieces of our application, whereas we will be dealing with employee management in a private area (later protected by a login page / user authentication, etc).

Inside your server.js add routes to respond to the following "get" requests for the application. Once you have written the routes, test that they work properly by returning a confirmation string using res.send() and testing the server using localhost:8080. For example, localhost:8080/managers could be set up to return something like "TODO: get all employees who have isManager==true". This will help to confirm that your routes are set up properly.

Important Note: Any response sending JSON from the server must include the correct content-type header - see res.json([body])

/employees

• This route will return a JSON formatted string containing all of the employees within the employees.json file
/managers

• This route will return a JSON formatted string containing all the employees whose isManager property is set to true.
/departments

• This route will return a JSON formatted string containing all of the departments within the departments.json file
[ no matching route ]

• If the user enters a route that is not matched with anything in your app (ie: http://localhost:8080/app) then you must return the custom message "Page Not Found" with an HTTP status code of 404.

Step 4: Writing the data-service.js module:

The promise driven data-service.js module will be responsible for reading the employees.json and departments.json files from within the "data" directory on the server, parsing the data into arrays of objects and returning elements (ie: "employee" objects) from those arrays to match queries on the data.
Essentially the data-service.js module will encapsulate all the logic to work with the data and only expose accessor methods to fetch data/subsets of the data.

Module Data
The following two arrays should be declared "globally" within your module:
• employees - type: array
• departments - type: array
Exported Functions
Each of the below functions are designed to work with the employees and departments datasets. Since we have no way of knowing how long each function will take (we cannot assume that they will be instantaneous, ie: what if we move from .json files to a remote database, or introduce hundreds of thousands of objects into our .json dataset? - this would increase lag time).

Because of this, every one of the below functions must return a promise that passes the data via it's "resolve" method (or - if no data was returned, passes an error message via it's "reject" method).

When we access these methods from the server.js file, we will be assuming that they return a promise and we will respond appropriately with .then() and .catch() (see "Updating the new routes…" below).

initialize()

• This function will read the contents of the "./data/employees.json" file (hint: see the fs module & the fs.readFile method), convert the file's contents into an array of objects (hint: see JSON.parse) , and assign that array to the employees array (from above).
• Only once the read operation for "./data/employees.json" has completed successfully (not before), repeat the process for the "./data/departments.json" and assign the parsed object array to the departments array from above.
• Once these two operations have finished successfully, invoke the resolve method for the promise to communicate back to server.js that the operation was a success.
• If there was an error at any time during this process, invoke the reject method for the promise and pass an appropriate message, ie: reject("unable to read file").
getAllEmployees()

• This function will provide the full array of "employee" objects using the resolve method of the returned promise.
• If for some reason, the length of the array is 0 (no results returned), this function must invoke the reject method and pass a meaningful message, ie: "no results returned".
getManagers()

• This function will provide an array of "employee" objects whose isManager property is true using the resolve method of the returned promise.
• If for some reason, the length of the array is 0 (no results returned), this function must invoke the reject method and pass a meaningful message, ie: "no results returned".
getDepartments()

• This function will provide the full array of "department" objects using the resolve method of the returned promise.
• If for some reason, the length of the array is 0 (no results returned), this function must invoke the reject method and pass a meaningful message, ie: "no results returned".

Step 5: Updating the code surrounding app.listen()

Before we start updating the routes in server.js to use our new data-service module, we must make a small update to the code surrounding the app.listen() call at the bottom of the server.js file. This is where the initialize() method from our data-service.js module comes into play.

Fundamentally, initialize() is responsible for reading the .json files from the "data" folder and parsing the results to create the "global" (to the module) arrays, "employees" and "departments" that are used by the other functions. However, it also returns a promise that will only resolve successfully once the files were read correctly and the "employees" and "departments" arrays were correctly loaded with the data.

Similarly, the promise will reject if any error occurred during the process. Therefore, we must only call app.listen() if our call to the initialize() method is successful, ie: .then(() => { //start the server }).
If the initialize() method invoked reject, then we should not start the server (since there will be no data to fetch) and instead a meaningful error message should be sent to the console, ie: .catch(()=>{ /*output the error to the console */})

Step 6: Updating the new routes to use data-service.js

Now that the data-service.js module is complete, we must update our new routes (ie: /employees, /managers & /departments) to make calls to the service and fetch data to be returned to the client. Recall: Any response sending JSON from the server must include the correct content-type header - see res.json([body]).

Since our data-service.js file exposes functions that are guaranteed to return a promise that (if resolved successfully), will contain the requested data, we must make use of the .then() method when accessing the data from within our routes.

For example, the /departments route must make a call to the getDepartments() method of the data-service.js module to fetch the correct data. If getDepartments() was successful, we can use .then((data) => { /*return JSON data*/ }) to access the data from the function and send the response back to the client.

If any of the methods were unsuccessful however, the .then() method will not be called - the catch() method will be called instead. If this is the case, the server must return a simple JSON object with 1 property:
"message" containing the message supplied in the .catch() method, ie: .catch((err) => { /* return err message in the JSON format: {message: err}*/ }).

By only calling res.json() from within .then() or .catch() we can ensure that the data will be in place (no matter how long it took to retrieve) before the server sends anything back to the client.

Step 7: Pusing to Heroku
• Once you are satisfied with your application, deploy it to Heroku:
o Ensure that you have checked in your latest code using git (from within Visual Studio Code) o Open the integrated terminal in Visual Studio Code o Log in to your Heroku account using the command heroku login o Create a new app on Heroku using the command heroku create o Push your code to Heroku using the command git push heroku master
• IMPORTANT NOTE: Since we are using an "unverified" free account on Heroku, we are limited to only 5 apps, so if you have been experimenting on Heroku and have created 5 apps already, you must delete one (or verify your account with a credit card). Once you have received a grade for Assignment 1, it is safe to delete this app (login to the Heroku website, click on your app and then click the Delete app… button under "Settings").

Testing: Sample Solution

To see a completed version of this app running, visit: https://sleepy-mesa-28798.herokuapp.com

Assignment Submission:
• Before you submit, consider updating site.css to provide additional style to the pages in your app. Black, White and Gray is boring, so why not add some cool colors and fonts (maybe something from Google Fonts)? This is your app for the semester, you should personalize it!
• Next, Add the following declaration at the top of your server.js file:
/********************************************************************************* * WEB322 – Assignment 02
*
*
* Online (Heroku) Link: ________________________________________________________
*
********************************************************************************/
• Submitted assignments must run locally, ie: start up errors causing the assignment/app to fail on startup will result in a grade of zero (0) for the assignment.
• Paste your Webapp’s Heroku URL in the Comments Section of the submissions page. Failure to do so will attract a -1.0 penalty.