js 监控浏览器关闭(完美兼容chrome & ie & fire fox)

 var UnloadConfirm = {};
 UnloadConfirm.MSG_UNLOAD = "数据尚未保存，离开后可能会导致数据丢失\n\n您确定要离开吗？";
 UnloadConfirm.set = function(a) {
     window.onbeforeunload = function(b) {
         b = b || window.event;
         b.returnValue = a;
         return a
     }
 };
 UnloadConfirm.clear = function() {
     fckDraft.delDraftById();
     window.onbeforeunload = function() {
     }
 };
 UnloadConfirm.set(UnloadConfirm.MSG_UNLOAD);

就是在ie浏览器  稍微有些敏感了.