Node.js and Express Mini Project

Topics:

• Client and server
• Node.js and Express
• HTTP requests and responses
• HTTP headers and status codes
• Request parameters
• API design and development

Description

You've been focusing on client-side JavaScript thus far, but now you'll make the transition to server-side. The goal here is to handle requests from the client and deliver back responses. In the mini project, you'll write an implementation of the game hangman that can be played by making HTTP requests!

Running the Project

• Run npm install to download the dependencies.
• Install nodemon via npm install -g nodemon. nodemon will keep your server running and automatically restart it if you change anything.
• Install Postman so you can make requests and examine responses.
• Run npm start to start the server.
• Implement hangman in src/app.js as per the instructions below.
• To test your application at any point, run npm start to start the server. Then, you can make requests to http://localhost:3000 in Postman or in your browser! To make POST requests, you'll need to use Postman. Craft the corrrect requests to play hangman and test your implementation!

Instructions

You'll develop a version of Hangman that can be played by making HTTP requests! First, some terminology:

• Final word: the final, correct word that the user is aiming to guess.
• Word so far: the word that the user currently sees based off his/her guesses. This is the final word with all non-guessed characters replaced by a dash '-'. For instance, if the final word is 'hello' and the user has guessed 'a', 'e', and 'i', the word so far would be '-e---'.

We've given you a function readWords() that reads an array of dictionary words from the words.txt file. First, use this function to select a random word from the dictionary to be the final word. Note that whenver your server is restarted (i.e. when you change files or re-run npm start), a new word will be selected and the game will restart.

Now, you'll need to implement two routes:

POST /guess

When the client makes a POST request to /guess:

• Ensure that the client provides letter in the request body. letter should be the key and the value should be a string containing only a single character. If there's an error, send an object of the form { error: "Error message" } as a JSON response. Make sure to respond with an appropriate status code.

• If the client has already guessed this letter, respond with an error in the same format as mentioned above.

• Keep track of the guess in some data structure. In the GET / route implementation (see below), you'll need to use this data structure to compute the word so far. Think carefully about what data structure you'd like to use here to make the computation easy.

GET /

When the client makes a GET request to /guess:

• Compute the word so far by replacing each letter in the final word that hasn't been guessed by -. Don't actually modify the final word in any way.

• Send back a JSON response containing an object with two properties, wordSoFar and guesses, to the client. wordSoFar should be the word so far (as per our definition underneath "Instructions"), and guesses should be the data structure you use to represent all guesses the user has made. This gives the user information about the current state of the game so he/she can formulate his/her next guess.

Play!

Now, you can play hangman by cycling through the requests above. Make a POST /guess request in Postman, passing in a letter in the request body. You can then see whether you guessed correctly, what the word so far is, and the list of guessed letters by requesting GET /. Keep guessing until you can figure out the word!

Extras

If you'd like an extra challenge (albeit not related to node/express), think about how you'd write a program to guess the word for you. Given the dictionary of words, how would you go about correctly guessing the final word? It's easy to simply guess every letter, but how could you do this efficiently? Is there a way to eliminate a large number of possible words with each guess?