JS控制浏览器刷新或退出显示提示语句

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);