var getDragClass=(function(){ var SupportsTouches = ("createTouch" in document),//判断是否支持触摸 StartEvent = SupportsTouches ? "touchstart" : "mousedown",//支持触摸式使用相应的事件替代
MoveEvent = SupportsTouches ? "touchmove" : "mousemove",
EndEvent = SupportsTouches ? "touchend" : "mouseup",
$=function(id){ return document.getElementById(id);
},
preventDefault=function(ev){ if(ev)ev.preventDefault();
else window.event.returnValue = false;
},
getMousePoint=function(ev){ var x = y = 0,
doc = document.documentElement,
body = document.body;
if(!ev) ev=window.event;
if (window.pageYoffset) { x = window.pageXOffset;
y = window.pageYOffset;
}else{ x = (doc && doc.scrollLeft || body && body.scrollLeft || 0) - (doc && doc.clientLeft || body && body.clientLeft || 0);
y = (doc && doc.scrollTop || body && body.scrollTop || 0) - (doc && doc.clientTop || body && body.clientTop || 0);
}
if(SupportsTouches){ var evt = ev.touches.item(0);//仅支持单点触摸,第一个触摸点
x=evt.pageX;
y=evt.pageY;
}else{ x += ev.clientX;
y += ev.clientY;
}
return { 'x' : x, 'y' : y}; };
function _drag(opt){ this.el=typeof opt.el=='string'?$(opt.el):opt.el;//被拖动节点
this.onstart=opt.start || new Function();//
this.onmove=opt.move || new Function();
this.οnend=opt.end || new Function();
this.action=false;
this.init();
}
_drag.prototype={ init:function(){ this.el.style.position='relative';
this.el['on'+StartEvent]=this.bind(function(e){ //绑定节点的 [鼠标按下/触摸开始] 事件 preventDefault(e);
if(this.action)return false;
else this.action=true;
this.startPoint=getMousePoint(e);
this.onstart();
document['on'+MoveEvent]=this.bind(function(e){ preventDefault(e);//取消文档的默认行为[鼠标移动、触摸移动]
this.nowPoint=getMousePoint(e);
this.el.style.left=this.nowPoint.x-this.startPoint.x+'px';
this.el.style.top=this.nowPoint.y-this.startPoint.y+'px';
this.onmove();
},this);
document['on'+EndEvent]=document['ontouchcancel']=this.bind(function(){ document['on'+EndEvent]=document['ontouchcancel']=document['on'+MoveEvent]=null;
this.action=false;
this.onend();
},this);
},this);
},
bind:function(fn,obj){ return function(){ fn.apply(obj,arguments);
}
}
}
return function(opt){ return new _drag(opt);
}
})();