事件代理啊

function bindEvent(obj, type, fn) {
    if (obj.addEventListener) {
      obj.addEventListener(type, eventFn);
    } else {
      obj.attachEvent("on" + type, eventFn);
    }

    function eventFn(ev) {
      var ev = ev || window.event;
      var target = ev.target || ev.srcElement;
      fn && fn(target, ev)
    }
  }