js添加事件、移除事件、阻止冒泡、阻止浏览器默认行为等写法(兼容IE/FF/CHROME)

var removeEvent = function( obj, type, fn ) {
  if (obj.removeEventListener)
      obj.removeEventListener( type, fn, false );
  else if (obj.detachEvent) {
      obj.detachEvent(  "on" +type, obj["e"+type+fn] );
      obj["e"+type+fn] = null;
  }
};

var stopEvent = function(e){
    e = e || window.event;
    if(e.preventDefault) {
      e.preventDefault();
      e.stopPropagation();
    }else{
      e.returnValue = false;
      e.cancelBubble = true;
    }
  },

var stopPropagation = function(e) {
   e = e || window.event;
  if (!+"\v1″) {
     e.cancelBubble = true;
  } else {
     e.stopPropagation();
  }
}

var  preventDefault  = function(e) {
    e = e || window.event;
    if(e.preventDefault) {
      e.preventDefault();
    }else{
      e.returnValue = false;
    }
}

var getEventTarget = function(e){
   e = e || window.event;
  var target = event.srcElement ? event.srcElement : event.target;
  return target;
}

var addPropertyChangeEvent = function (obj,fn) {
  if(window.ActiveXObject){
      obj.onpropertychange = fn;
  }else{
      obj.addEventListener("input",fn,false);
  }
}