code: function getButtons( hammerEvent ) {
      if ( !hammerEvent || !hammerEvent.srcEvent ) return 0;
      const buttons = hammerEvent.srcEvent.buttons;
      if ( typeof buttons === 'number' ) return buttons;
      return 0;
  }
docs: Get the information on buttons pressed.
  This is a cumulative value because several buttons can be pressed at the same time:
  1: left mouse button.
  2: right mouse button.
  4: middle mouse button.
  Then, if the result is 3 (1+2), it means that the left and the right mouse buttons are pressed.
  
  @param {object} hammerEvent - Hammer event.
  @param {integer} hammerEvent.srcEvent.buttons - The information we need.
  @returns {integer} A betwise OR of the pressed buttons.