code: function touchEnd(element, clientX, clientY) {
    element[symbols.dragging] = false;
    if (element[deltaXSymbol] >= 20) {
      // Finished going right at high speed.
      element[symbols.goLeft]();
    } else if (element[deltaXSymbol] <= -20) {
      // Finished going left at high speed.
      element[symbols.goRight]();
    } else {
      // Finished at low speed.
      trackTo(element, clientX);
      const travelFraction = element.travelFraction;
      if (travelFraction >= 0.5) {
        element[symbols.goRight]();
      } else if (travelFraction <= -0.5) {
        element[symbols.goLeft]();
      }
    }
    element.travelFraction = 0;
    element[deltaXSymbol] = null;
    element[deltaYSymbol] = null;
  }
docs: /*
  Invoked when the user has finished a touch operation.