function touchstart() {
    start.apply(this, arguments);
    var touches = d3_behavior_zoomTouchup(),
        touch,
        now = Date.now();
    if ((touches.length === 1) && (now - d3_behavior_zoomLast < 300)) {
      d3_behavior_zoomTo(1 + Math.floor(xyz[2]), touch = touches[0], d3_behavior_zoomLocations[touch.identifier]);
    }
    d3_behavior_zoomLast = now;
  }
function touchstart() {
    start.apply(this, arguments);
    var touches = d3_behavior_zoomTouchup(),
        touch,
        now = Date.now();
    if ((touches.length === 1) && (now - d3_behavior_zoomLast < 300)) {
      d3_behavior_zoomTo(1 + Math.floor(xyz[2]), touch = touches[0], d3_behavior_zoomLocations[touch.identifier]);
    }
    d3_behavior_zoomLast = now;
  }
function touchstart ( ) { start . apply ( this , arguments ) ; var touches = d3_behavior_zoomTouchup ( ) , touch , now = Date . now ( ) ; if ( ( touches . length === 1 ) && ( now - d3_behavior_zoomLast < 300 ) ) { d3_behavior_zoomTo ( 1 + Math . floor ( xyz [ 2 ] ) , touch = touches [ 0 ] , d3_behavior_zoomLocations [ touch . identifier ] ) ; } d3_behavior_zoomLast = now ; }
doubletap detection
doubletap detection