ajax重写设置全局header

_ajax = $.ajax;

$.ajax = function (opt) {
    return getPati(function (pati) {
        var fn, _opt;
        fn = {
            beforeSend: function (request) {}
        };
        if (opt.beforeSend) {
            fn.beforeSend = opt.beforeSend;
        }
        _opt = $.extend(opt, {
            beforeSend: function (request) {
                request.setRequestHeader("X-Pati", pati);
                request.setRequestHeader("X-PageCode", $('#pageCode').val());
                return fn.beforeSend(request);
            }
        });
        return _ajax(_opt);
    });
};