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Learn RxJS
Memory Game
This recipe demonstrates an RxJS game to train your memory.
Example Code
Memory Game
index.ts
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// RxJS v6+
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import { EMPTY, from, fromEvent, generate, interval, merge, noop } from 'rxjs';
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import {
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map,
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pluck,
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scan,
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sequenceEqual,
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switchMap,
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take,
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tap
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} from 'rxjs/operators';
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​
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const random = (): number => Math.floor(Math.random() * Math.floor(8));
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const setInfo = (text: string) =>
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(document.getElementById('info').innerHTML = text);
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const displayLevelChange = () =>
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document
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.querySelectorAll('.child')
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.forEach((c: HTMLElement) => (c.style.background = 'gray'));
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​
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const checkIfGameOver$ = (randomSequence: number[]) => (
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userSequence: number[]
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) =>
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from(userSequence).pipe(
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sequenceEqual(from(randomSequence)),
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tap(match =>
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!match && userSequence.length === randomSequence.length
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? setInfo('GAME OVER!')
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: noop
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)
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);
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​
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const takePlayerInput$ = (randomSequence: number[]) => _ =>
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fromEvent(document, 'click').pipe(
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take(randomSequence.length),
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scan(
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(acc: number[], curr: MouseEvent) => [
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...acc,
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parseInt(curr.target['id'])
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],
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[]
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),
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switchMap(checkIfGameOver$(randomSequence)),
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switchMap(result =>
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result
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? (displayLevelChange(), memoryGame$(randomSequence.length + 1))
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: EMPTY
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)
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);
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​
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const showSequenceToMemorize$ = (memorySize: number) => (
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randomSequence: number[]
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) =>
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interval(1000).pipe(
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tap(i =>
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setInfo(i === memorySize - 1 ? `YOUR TURN` : `${memorySize - i} elements`)
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),
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take(randomSequence.length),
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map(index => randomSequence[index]),
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tap(value => document.getElementById(`${value}`).click()),
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switchMap(takePlayerInput$(randomSequence))
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);
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​
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const memoryGame$ = memorySize =>
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generate(
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1,
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x => x <= memorySize,
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x => x + 1
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).pipe(
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scan((acc: number[], _: number): number[] => [...acc, random() + 1], []),
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switchMap(showSequenceToMemorize$(memorySize))
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);
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​
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const elementClick$ = (event: string, color: string) =>
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fromEvent(document.querySelectorAll('.child'), event).pipe(
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pluck('srcElement'),
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tap((e: HTMLElement) => (e.style.background = color))
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);
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​
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const clicks$ = merge(
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elementClick$('click', 'lightgray'),
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elementClick$('transitionend', 'white')
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);
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​
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const game$ = merge(clicks$, memoryGame$(2));
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​
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game$.subscribe();
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index.html
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<style>
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.parent {
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border-spacing: 5px;
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width: 50%;
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padding: 0.5em;
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}
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​
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.parent.perspective {
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perspective: 50em;
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}
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​
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.child {
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margin: 0.5em;
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max-width: 2em;
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min-width: 2em;
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height: 2.8em;
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padding: 0.5em;
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display: table-cell;
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border: 1px solid rgba(0, 0, 0, 0.5);
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}
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​
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.parent.perspective .child {
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transform: rotateX(40deg);
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transition: all 0.3s ease-in;
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}
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</style>
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​
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<div id="info">Train Your Memory!</div>
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<div id="grid" class="grid parent perspective">
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<div>
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<div class="child" id="1"></div>
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<div class="child" id="2"></div>
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<div class="child" id="3"></div>
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</div>
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<div>
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<div class="child" id="4"></div>
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<div class="child" id="5"></div>
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<div class="child" id="6"></div>
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</div>
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<div>
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<div class="child" id="7"></div>
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<div class="child" id="8"></div>
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<div class="child" id="9"></div>
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</div>
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</div>
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Operators Used
Last modified 2yr ago
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