jump-ability.js

const ACCEL_G = -9.8, // m/s^2
    EASING = -15; // m/s^2

/**
 * Jump ability.
 */
module.exports = AFRAME.registerComponent('jump-ability', {
  dependencies: ['velocity'],

  /* Schema
  ——————————————————————————————————————————————*/

  schema: {
    on: { default: 'keydown:Space gamepadbuttondown:0' },
    playerHeight: { default: 1.764 },
    maxJumps: { default: 1 },
    distance: { default: 5 },
    debug: { default: false }
  },

  init: function () {
    this.velocity = 0;
    this.numJumps = 0;

    const beginJump = this.beginJump.bind(this),
        events = this.data.on.split(' ');
    this.bindings = {};
    for (let i = 0; i <  events.length; i++) {
      this.bindings[events[i]] = beginJump;
      this.el.addEventListener(events[i], beginJump);
    }
    this.bindings.collide = this.onCollide.bind(this);
    this.el.addEventListener('collide', this.bindings.collide);
  },

  remove: function () {
    for (var event in this.bindings) {
      if (this.bindings.hasOwnProperty(event)) {
        this.el.removeEventListener(event, this.bindings[event]);
        delete this.bindings[event];
      }
    }
    this.el.removeEventListener('collide', this.bindings.collide);
    delete this.bindings.collide;
  },

  beginJump: function () {
    if (this.numJumps < this.data.maxJumps) {
      const data = this.data,
          initialVelocity = Math.sqrt(-2 * data.distance * (ACCEL_G + EASING)),
          v = this.el.getAttribute('velocity');
      this.el.setAttribute('velocity', {x: v.x, y: initialVelocity, z: v.z});
      this.numJumps++;
      this.el.emit('jumpstart');
    }
  },

  onCollide: function () {
    if (this.numJumps > 0) this.el.emit('jumpend');
    this.numJumps = 0;
  }
});