Frage zum Wiki-Artikel „Pointer Events“, Nachbesserung

[JürgenB]

Hallo Beat,

So diesmal eine getestete Version

var eventSupport={
   'pointerdown': ('onpointerdown' in window)? true : false,
   'mousedown': ('onmousedown' in window)? true : false,
   // ...
};
//console.log(eventSupport);
function pickEvent(chooseFrom){
   while(chooseFrom.length > 0){
      var type = chooseFrom.shift();
      if(eventSupport[type] == true ) return type;
   }
}

// später
var el = document.body;
//console.log(el);
//console.log(pickEvent(["pointerdown","mousedown"]));
el.addEventListener(pickEvent(["pointerdown","mousedown"]), 
                    function(ev){console.log(ev);} 
);

jetzt fehlt nur noch der touchstart. Im Wiki-Artikel sieht es dann so aus:

// Ermitteln der unterstützten Methoden  
  var can_touch = ("TouchEvent" in window);
  var can_pointer = ("PointerEvent" in window);

// Die Eventhandler für pointer-, touch- und mouse-Events setzen
  if(can_pointer) { 
    roi.style.touchAction = "none";
    roi.addEventListener("pointerdown",start_roi,false);
    roi.addEventListener("pointermove",move_pointer,false);
    roi.addEventListener("pointerup",end_move,false);
  }
  else {
    if(can_touch) {
      roi.addEventListener("touchstart",start_roi,false);
      roi.addEventListener("touchmove",move_touch,false);
      roi.addEventListener("touchend",end_move,false);
    }
    roi.addEventListener("mousedown",start_roi,false);
    roi.addEventListener("mousemove",move_mouse,false);
    roi.addEventListener("mouseup",end_move,false);
  }

Gruß
Jürgen