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Platform Jumper Game
This recipe demonstrates RxJS implementation of Platform Jumper game.
Example Code
Platform Jumper
index.ts
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// RxJS v6+
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import { interval, of, fromEvent, combineLatest } from 'rxjs';
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import { scan, tap, startWith, pluck, switchMap, takeWhile } from 'rxjs/operators';
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import { gameSize } from './constants';
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import { render } from './html-renderer';
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import { Player, Platform } from './interfaces';
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import { updatePlayer, updatePlatforms, initialPlatforms, initialPlayer, handleCollisions, handleKeypresses } from './game';
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​
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const gameSpeed = 500;
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​
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const platforms$ = interval(gameSpeed)
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.pipe(
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scan<number, Platform[]>(updatePlatforms, initialPlatforms)
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);
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​
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const keys$ = (initialPlayer: Player) => fromEvent(document, 'keydown')
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.pipe(
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startWith({ key: '' }),
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pluck('key'),
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scan<string, Player>(
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(plyr: Player, key: string) => handleKeypresses(plyr, key),
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initialPlayer
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)
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);
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​
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const player$ = of(initialPlayer())
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.pipe(
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switchMap(p => combineLatest(interval(gameSpeed / 4), keys$(p))
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.pipe(
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scan<[number, Player], Player>((_, [__, player]) => updatePlayer(player))
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)),
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);
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​
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combineLatest(player$, platforms$)
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.pipe(
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scan<[Player, Platform[]], [Player, Platform[]]>(
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(_, [player, platforms]) => handleCollisions([player, platforms])),
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tap(render),
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takeWhile(([player, platforms]) => player.lives > 0)
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)
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.subscribe()
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game.ts
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import { Player, Platform } from './interfaces';
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import { gameSize } from './constants';
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​
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const newPlatform = (x, y): Platform => ({ x, y, scored: false });
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const newPlayer = (x, y, jumpValue, score, lives): Player => ({
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x,
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y,
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jumpValue,
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canJump: false,
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score: score,
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lives: lives
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});
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const startingY = 4;
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export const initialPlayer = (): Player => newPlayer(0, startingY, 0, 0, 3);
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export const initialPlatforms = [newPlatform(gameSize / 2, startingY)];
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​
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const random = y => {
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let min = Math.ceil(y - 4);
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let max = Math.floor(y + 4);
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min = min < 0 ? 0 : min;
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max = max > gameSize - 1 ? gameSize - 1 : max;
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​
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return Math.floor(Math.random() * (max - min + 1)) + min;
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};
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​
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export const updatePlatforms = (platforms: Platform[]): Platform[] => (
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platforms[platforms.length - 1].x > gameSize / 5
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? platforms.push(newPlatform(1, random(platforms[platforms.length - 1].y)))
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: () => {},
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platforms.filter(e => e.x < gameSize - 1).map(e => newPlatform(e.x + 1, e.y))
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);
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​
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export const handleKeypresses = (player: Player, key: string) =>
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key === 'ArrowRight'
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? newPlayer(
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player.x,
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player.y + (player.y < gameSize - 1 ? 1 : 0),
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player.jumpValue,
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player.score,
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player.lives
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)
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: key === 'ArrowLeft'
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? newPlayer(
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player.x,
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player.y - (player.y > 0 ? 1 : 0),
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player.jumpValue,
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player.score,
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player.lives
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)
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: key === 'ArrowUp'
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? newPlayer(
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player.x,
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player.y,
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player.x === gameSize - 1 || player.canJump ? 6 : 0,
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player.score,
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player.lives
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)
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: player;
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​
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export const updatePlayer = (player: Player): Player => (
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(player.jumpValue -= player.jumpValue > 0 ? 1 : 0),
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(player.x -= player.x - 3 > 0 ? player.jumpValue : 0),
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(player.x += player.x < gameSize - 1 ? 1 : 0),
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player.x === gameSize - 1 ? ((player.lives -= 1), (player.x = 1)) : () => {},
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player
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);
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​
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const handleCollidingPlatform = (
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collidingPlatform: Platform,
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player: Player
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) => {
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if (player.canJump) {
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return;
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}
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​
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if (!collidingPlatform) {
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player.canJump = false;
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return;
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}
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​
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if (!collidingPlatform.scored) {
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player.score += 1;
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}
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collidingPlatform.scored = true;
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​
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player.canJump = true;
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};
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​
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export const handleCollisions = ([player, platforms]: [Player, Platform[]]): [
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Player,
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Platform[]
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] => (
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handleCollidingPlatform(
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platforms.find(p => p.x - 1 === player.x && p.y === player.y),
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player
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),
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(player.x = player.canJump
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? (collidingPlatforms =>
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collidingPlatforms.length
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? (platform => platform.x - 1)(
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collidingPlatforms[collidingPlatforms.length - 1]
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)
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: player.x)(
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platforms.filter(p => p.y === player.y && p.x >= player.x)
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)
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: player.x),
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[player, platforms]
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);
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interfaces.ts
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export interface Player {
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x: number;
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y: number;
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jumpValue: number;
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canJump: boolean;
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score: number;
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lives: number;
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}
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​
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export interface Platform {
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x: number;
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y: number;
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scored: boolean;
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}
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constants.ts
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export const gameSize = 20;
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html-renderer.ts
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import { gameSize } from './constants';
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import { Player, Platform } from './interfaces';
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​
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export const render = ([player, platforms]: [Player, Platform[]]) => {
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document.body.innerHTML = `Lives: ${player.lives} Score: ${player.score} </br>`;
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​
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const game = Array(gameSize)
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.fill(0)
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.map(_ => Array(gameSize).fill(0));
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game[player.x][player.y] = '*';
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platforms.forEach(p => (game[p.x][p.y] = '_'));
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​
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game.forEach(r => {
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r.forEach(c => (document.body.innerHTML += c === 0 ? '...' : c));
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document.body.innerHTML += '<br/>';
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});
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};
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Operators Used
Last modified 2yr ago