gamepad-rxjs

A class to use the Gamepad API with RxJs Observables

Polls the Gamepad state every 15ms to emit button presses/releases or joystick movements.

Install

$ npm install gamepad-rxjs;

Usage

import {
  GamepadObservables,
  ButtonEvent,
  JoystickDirectionEvent,
} from 'gamepad-rxjs';
import { merge, filter, throttle, interval, map, pairwise } from 'rxjs';

const player1 = new GamepadObservables(0);
const player2 = new GamepadObservables(1);

// emits only when the button's state changes
// refer to the Gamepad API documentation for the button mappings
merge(player1.buttonPressed$(9), player1.buttonReleased$(9)).subscribe(
  ({ current }: ButtonEvent) => {
    console.log(
      `Player 1 just ${
        current.pressed ? 'pressed' : 'released'
      } the start button!`
    );
  }
);

// every observable emits both the previous and current button states
// this one provides the joystick's angle and pressure (distance from the center,
// a decimal number from 0 to 1) instead of its x and y coordinates
player2
  .joystickDirection$(0)
  .pipe(
    map(({ previous, current }: JoystickDirectionEvent) => {
      const delta = Math.round((previous.angle - current.angle) * 100) / 100;
      const quadrantPrevious = ~~(previous.angle / 90) + 1;
      const quadrantCurrent = ~~(current.angle / 90) + 1;

      return (quadrantPrevious === 1 && quadrantCurrent === 4) ||
        (delta > 0 && !(quadrantPrevious === 4 && quadrantCurrent === 1))
        ? 'clockwise'
        : 'counterclockwise';
    }),
    pairwise(),
    filter(([previous, current]) => previous !== current),
    map(([_, current]) => current)
  )
  .subscribe((motion: 'clockwise' | 'counterclockwise') => {
    console.log(`Player 2 rotated the left joystick ${motion}.`);
  });

// since all the other observables will emit only once a button is pressed or once
// a joystick angle has changed, you can use this observable which polls the gamepad's
// state every 15ms to obtain the gamepad's current state
player1.gamepadEvent$
  .pipe(throttle(() => interval(5000)))
  .subscribe((gamepad: Gamepad) => {
    console.log(`This is a snapshot of Player 1's gamepad state: `, gamepad);
  });