By adamlubek
This recipe demonstrates an RxJS implementation of Breakout game.
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// RxJS v6+
import { fromEvent, of, interval, combineLatest, generate, noop } from 'rxjs';
import { map, mergeMap, pluck, startWith, scan, toArray, takeWhile, tap } from 'rxjs/operators';
import { gameSize } from './constants';
import { Player, Ball, GameObject } from './interfaces';
import { render } from './html-renderer';
const createGameObject = (x, y) => ({ x, y });
const player$ = combineLatest(
of({ ...createGameObject(gameSize - 2, (gameSize / 2) - 1), score: 0, lives: 3 }),
fromEvent(document, 'keyup').pipe(startWith({ code: '' }), pluck('code'))
).pipe(
map(([player, key]) => (
key === 'ArrowLeft'
? player.y -= 1
: key === 'ArrowRight'
? player.y += 1
: noop
, player)
)
)
const ball$ = combineLatest(
of({ ...createGameObject(gameSize / 2, (gameSize - 3)), dirX: 1, dirY: 1 }),
interval(150)
).pipe(
map(([ball, _]: [Ball, number]) => (
ball.dirX *= ball.x > 0 ? 1 : -1,
ball.dirY *= (ball.y > 0 && ball.y < gameSize - 1) ? 1 : -1,
ball.x += 1 * ball.dirX,
ball.y -= 1 * ball.dirY,
ball)
)
)
const bricks$ = generate(1, x => x < 8, x => x + 1)
.pipe(
mergeMap(r => generate(r % 2 === 0 ? 1 : 0, x => x < gameSize, x => x + 2)
.pipe(map(c => createGameObject(r, c)))
),
toArray()
)
const processGameCollisions = (_, [player, ball, bricks]: [Player, Ball, GameObject[]])
: [Player, Ball, GameObject[]] => (
(collidingBrickIndex => collidingBrickIndex > -1
? (bricks.splice(collidingBrickIndex, 1), ball.dirX *= -1, player.score++)
: noop
)(bricks.findIndex(e => e.x === ball.x && e.y === ball.y)),
ball.dirX *= player.x === ball.x && player.y === ball.y ? -1 : 1,
ball.x > player.x ? (player.lives-- , ball.x = (gameSize / 2) - 3) : noop,
[player, ball, bricks]
)
combineLatest(player$, ball$, bricks$)
.pipe(
scan<[Player, Ball, GameObject[]], [Player, Ball, GameObject[]]>(processGameCollisions),
tap(render),
takeWhile(([player]: [Player, Ball, GameObject[]]) => player.lives > 0)
).subscribe()export interface GameObject {
x: number;
y: number;
}
export interface Player extends GameObject {
score: number;
lives: number;
}
export interface Ball extends GameObject {
dirX: number;
dirY: number;
}export const gameSize = 20;import { gameSize } from './constants';
import { Player, Ball, GameObject } from './interfaces';
const empty = 0;
const plyer = 1;
const bll = 2;
const brick = 3;
const createElem = col => {
const elem = document.createElement('div');
elem.classList.add('board');
elem.style.display = 'inline-block';
elem.style.marginLeft = '10px';
elem.style.height = '6px';
elem.style.width = '6px';
elem.style['background-color'] =
col === empty
? 'white'
: col === plyer
? 'cornflowerblue'
: col === bll
? 'gray'
: 'silver';
elem.style['border-radius'] = col === bll ? '100%' : '0%';
return elem;
};
export const render = ([player, ball, bricks]: [
Player,
Ball,
GameObject[]
]) => {
const game = Array(gameSize)
.fill(0)
.map(e => Array(gameSize).fill(0));
game[player.x][player.y] = plyer;
game[ball.x][ball.y] = bll;
bricks.forEach(b => (game[b.x][b.y] = brick));
document.body.innerHTML = `Score: ${player.score} Lives: ${player.lives} <br/>`;
game.forEach(r => {
const rowContainer = document.createElement('div');
r.forEach(c => rowContainer.appendChild(createElem(c)));
document.body.appendChild(rowContainer);
});
};