Exercise 4

You are asked to improve the Game class and to implement and test the keyboard(listener) function. Notice that some design decisions, such as the introduction of a Message class, depend on the multiplayer features that will be implemented in the future assignments.

Message class

The Message class corresponds to the inputs generated by the user when pressing the keyboard. They are generated by the keyboard(listener) function and handled by the Game.onMessage(id, message) method. Later on, messages will be serialized and transmitted over the network.

Game class

The Game class extends the Map class to store moving entities. The identifiers (id) of the moving entities act as keys in the map. Hence, the set(id, entity), get(id) and delete(id) methods provided by the Map class can be used in the Game class to manage the moving entities during their lifecycle. You are asked to implement several methods in the Game class according to the tests provided in test/game.js. The tests are provided as guidelines and do not cover all the corner cases.

Keyboard function

In JavaScript, pressing a key results in several successive keydown events, i.e., consecutive events are triggered until the key goes up again (keyup event). The keyboard function is responsible for listening to the keybord (with window.addEventListener), for stopping the propagation of events, and for filtering duplicated events. The parameter of the keyboard function is a listener function that takes a message as a parameter. A messageis an instance of the Message class created with the event.type and event.key properties of a keyboard event. You can use the Set class of the standard library to filter consecutive events. You are asked to implement the keyboard(listener) function and to provide meaninful unit tests in the test/keyboard.js file and a few line of documentation explaining your choices.

Evaluation

All your modifications should take place in the files src/game.js, src/keyboard.js, and test/keyboard.js files, which contain TODO placeholders. For the corrections, we will check that your project passes the provided tests. Additionally, we will read the tests you created and visually verify in the browser that the game behaves as in the demonstration.

Prerequisites

• Node 16 (LTS)

Setup

Install project dependencies

npm install

Start the server

npm run start

# or start server in watch mode
# so it automatically restarts on file changes
npm run watch

Run tests

npm run test

See more in the scripts section of your package.json.