3.4 KiB
Battleships!
A backend implementation Battleship using JavaScript.
Setup
You will need to have the prompt-sync module for synchronous prompting of user input:
npm install --save prompt-sync
Clone the repo, navigate to the directory, and run:
node app.js
Simple as that! For placing ships, enter coordinates in the form [x,y], for attacking ships, use [y,x]
Design
Battleships uses an object-oriented approach to game design:
Classes
Player
Has a name, board, and collection of ships. Giving each player a board allows us to abstract the board logic to its own class, and define a set of functions that will work regardless of the state of the current player's board.
Player has one instance method on its prototype – lost() which makes use of ES6's Array.prototype.every() function to check if all ships in the collection are sunk.
Ship
Ships have a name, length, and numHits. The ship uses 4 static methods to create instances of itself:
Ship.aircraftCarrier = function() {
return new Ship(5, "aircraft carrier")
};
This allows the Player class to have ships like so:
Player.prototype.createShips = function() {
return (
{
aircraftCarrier: Ship.aircraftCarrier(),
battleship: Ship.battleship(),
submarine: Ship.submarine(),
patrolBoat: Ship.patrolBoat()
}
)
};
Ships have a hit() method, which increments numHits and checks its sunk() method.
Board
The board manages the placement of ships, checking if an attack hits or misses, and creation of the obfuscated board.
Ships are represented on the board as letters. For example, aircraft carriers are represented by the letter 'a'. The board iterates over its cells and uses a switch statement to handle a successful hit:
if (target != 'x' && target != '~') {
console.log("It's a hit!");
switch (target) {
case 'a':
player.ships.aircraftCarrier.hit();
break;
case 'b':
player.ships.battleship.hit();
break;
case 's':
player.ships.submarine.hit();
break;
case 'p':
player.ships.patrolBoat.hit();
break;
}
obfuscateBoard() is used to display the 'upper' board of the player, which is essentially (for now) a record of successful hits. During a given players turn, they will see their opponents obfuscated board. Board obfuscation is accomplished by making a deep copy of the board and replacing anything other than an 'x' (a hit) with '~'
Board.prototype.obfuscateBoard = function() {
let deepCopy = JSON.parse(JSON.stringify(this.cells));
deepCopy.forEach( (row, i) => {
row.forEach( (el, j) => {
if (el !== 'x' && el !== '~') {
deepCopy[i][j] = '~';
}
});
});
return deepCopy;
}
app
The game driver, app.js, is not actually a class. It is a collection of functions mainly used to set up the game and maintain the rules with validation of coordinates, checking if the game is over, etc. It instantiates two players and then calls gameSetup() once for each player followed by playGame()
Validation is tricky. There are many ways for a user to give bad input. validCoords() stops four behaviors: placing ships diagonally, placing ships out of bounds, placing ships on top of one another, placing ships in a space that is too small or large for the given ship.