对$.ajax重写，增强处理

// 首先备份下jquery的ajax方法
var _ajax = $.ajax;

// 重写jquery的ajax方法
$.ajax = function (options) {
    var _opt = {
        beforeSend: function (xhr) {
            if (options.beforeSend) options.beforeSend(xhr);
        },
        success: function (result, status, xhr) {
            if (options.success) options.success(result, status, xhr);
        },
        error: function (xhr, status, error) {
            switch (xhr.status) {
                case 403:
                    layer.alert('服务器拒绝提供服务', {icon: 2, title: '错误信息'});
                    break;
                case 404:
                    layer.alert('请求的资源不存在', {icon: 2, title: '错误信息'});
                    // location.href = '404.html';
                    break;
                case 500:
                    layer.alert('服务器发生不可预期的错误', {icon: 2, title: '错误信息'});
                    // location.href = '500.html';
                    break;
                case 503:
                    layer.alert('服务器繁忙，请稍后再试', {icon: 2, title: '错误信息'});
                    break;
            }
            if (options.error) options.error(xhr, status, error);
        },
        complete: function (xhr, status) {
            if (options.complete) options.complete(xhr, status);
        }
    };

    // 返回重写的ajax
    return _ajax($.extend({}, _opt, options));
};

不重新$.ajax，重新options

var utils = {
    ajax: function (options) {
        var _opt = {
            beforeSend: function (xhr) {
                if (options.beforeSend) return options.beforeSend(xhr);
            },
            success: function (result, status, xhr) {
                // 登录过期
                // if (result != undefined && result.statusCode === "1000") {
                //     location.href = "index.html";
                // }
                if (options.success) return options.success(result, status, xhr);
            },
            error: function (xhr, status, error) {
                switch (xhr.status) {
                    case 403:
                        layer.alert('服务器拒绝提供服务', {icon: 2, title: '错误信息'});
                        break;
                    case 404:
                        layer.alert('请求的资源不存在', {icon: 2, title: '错误信息'});
                        // location.href = '404.html';
                        break;
                    case 500:
                        layer.alert('服务器发生不可预期的错误', {icon: 2, title: '错误信息'});
                        // location.href = '500.html';
                        break;
                    case 503:
                        layer.alert('服务器繁忙，请稍后再试', {icon: 2, title: '错误信息'});
                        break;
                }
                if (options.error) return options.error(xhr, status, error);
            },
            complete: function (xhr, status) {
                if (options.complete) return options.complete(xhr, status);
            }
        };
        var _options = $.extend({}, options, _opt);
        $.ajax(_options);
    }
}