code: function WorkerDriver (options) {
    this.fps = options.fps;
    this.engine = options.engine;
    this.interpolate = options.interpolate;
    // Approximate number of physics steps to 'pad' rendering.
    this.interpBufferSize = options.interpolationBufferSize;
    this.debug = options.debug;
  
    this.bodies = {};
    this.contacts = [];
  
    // https://gafferongames.com/post/snapshot_interpolation/
    this.frameDelay = this.interpBufferSize * 1000 / this.fps;
    this.frameBuffer = [];
  
    this.worker = this.debug
      ? webworkifyDebug(worker)
      : webworkify(worker);
    this.worker.addEventListener('message', this._onMessage.bind(this));
  }
docs: ****************************************************************************
  Constructor