JQuery Plugin for poll message notification

jquery-poll-message.js

/*
    JQuery Plugin for poll message from RESTful API
    
    Usage:
        [HTML]
            <a href="javascript:void;" id="msgText"></a>

        [JavaScript]
            $('#msgText').pollMessage({
                'url': '/newmessage/get',
                'duration': 10,
                'click': function (msg) {
                    console.log(msg);
                }
            }).start();

        [Expected JSON]
            {
                hasError [bool],
                error [string],
                data [string]
            }

*/
(function ($) {
    $.fn.pollMessage = function (options) {

        var isStop = false,
            settings = {},
            curMessage = {}
            that = this;

        function _displayMessage(msg) {
            if (!msg.hasError) {
                that.html("你有" + msg.data + "条新消息");
            } else {
                that.html("错误:" + msg.error);
            }
        }

        function _poll() {
            $.ajax({
                type: "GET",
                url: settings.url,
                cache: false,
                success: function (jsonMsg) {
                    msg = $.parseJSON(jsonMsg);
                    curMessage = msg;

                    settings.newMessage.apply(that, [msg]);
                    if (!isStop) {
                        setTimeout(_poll, settings.duration * 1000);
                    }
                },
                error: function (XMLHttpRequest, textStatus, errorThrown) {
                    settings.error.apply(that, [{ 'hasError': true, 'error': '无法连接', 'data': '' }]);
                    if (!isStop) {
                        setTimeout(_poll, settings.duration * 1000);
                    }
                }
            });
        }

        function start() {
            isStop = false;
            setTimeout(_poll, 500);
        }

        function stop() {
            isStop = true;
        }

        function setOptions(opts) {
            settings = $.extend({
                'url': './Handlers/NewMessageHandler.ashx',
                'duration': 5,
                'newMessage': _displayMessage,
                'error': _displayMessage,
                'click': function(){}
            }, options);
        }

        //init
        setOptions(options);

        that.click(function () {
            settings.click.apply(that, [curMessage]);    
            return false;
        });
        return {
            'start': start,
            'stop': stop,
            'setOptions': setOptions
        }

    };
})(jQuery);