【JS】判断touch方向

check-touch-direction.js

/** 
  obj:触发元素； 
  dir:期望触发方向；'up','down','left','right' 
  fn :触发后的回调函数 
*/  
var touchEvent = function(obj,dir,fn){  
    this.pos = {x:0,y:0};//开始触发位置  
    var me = this;  
    obj.addEventListener('touchstart',function(event){  
        var touch = event.touches[0];  
        me.pos.x = touch.pageX;  
        me.pos.y = touch.pageY;  
    },false);  
    obj.addEventListener('touchmove',function(event){  
        var touch = event.touches[0];  
        me.curtouch = {  
            x:touch.pageX,  
            y:touch.pageY  
        }  
    },false);  
    obj.addEventListener('touchend',function(event){  
        if(me.checkDirV(me.pos,me.curtouch)==dir ||me.checkDirH(me.pos,me.curtouch)==dir){  
            (typeof fn=='function')&&fn();  
        }  
    },false);     
}  
touchEvent.prototype = {  
    posdiff:100,//触发敏感度  
    checkDirV:function(a,b){  
        return Math.abs(a.y-this.posdiff)>b.y?(a.y>b.y?'up':'down'):'';  
    },  
    checkDirH:function(a,b){  
        return Math.abs(a.x-this.posdiff)>b.x?(a.x>b.x?'left':'right'):'';  
    }  
}  


////eg:new touchEvent(document.getElementById('content'),'left',function(){alert(34);});