move.js

import engine from '../engine';
import system from '../system';

import input from '../components/input';
import position from '../components/position';
import velocity from '../components/velocity';

export default system([ input, position, velocity ], entity => {
    const { keyboard } = engine;
    const { controls } = input.of(entity);
    const { x, y } = position.of(entity);

    if (keyboard.get(controls.up)) {
        velocity.update(entity, { y: -1 });
    }

    if (keyboard.get(controls.right)) {
        velocity.update(entity, { x: 1 });
    }

    if (keyboard.get(controls.down)) {
        velocity.update(entity, { y: 1 });
    }

    if (keyboard.get(controls.left)) {
        velocity.update(entity, { x: -1 });
    }
  
    const { x: vx, y: vy } = velocity.of(entity);

    position.update(entity, {
        x: x + vx,
        y: y + vy
    });
});