The last several lines. It said that s, msg and base header was undefined.

prob with callback.js

/**
 * Created with JetBrains WebStorm.
 * User: xadillax
 * Date: 7/14/13
 * Time: 9:44 PM
 * NBUT Online Judge Impl.
 */
var base = require("../base");
var util = require("util");

/**
 * Create an NOJ Module
 * @param baseurl
 * @returns {nbut}
 */
exports.create = function(baseurl) {
    return new nbut(baseurl);
}

/**
 * The NOJ Module
 * @param baseurl
 */
function nbut(baseurl) {
    base.core.call(this);

    this.name = "NOJ";
    this.logger = base.logger("NOJ");
    if(undefined === baseurl) {
        this.baseurl = "http://acm.nbut.edu.cn/";
    }
}

util.inherits(nbut, base.core);

/**
 * Overwrite and ignore the base.
 * @param username
 * @param password
 */
nbut.prototype.login = function(username, password, callback) {
    var url = this.baseurl + "user/chklogin.xhtml";
    var data = {
        "username" : username,
        "password" : password
    };
    var datalen = base.util.getDataLength(data);
    var header = {
        "content-type"      : "application/x-www-form-urlencoded",
        "content-length"    : datalen,
        "user-agent"        : this.getUserAgent()
    };

    this.logger.info("Login NOJ: [ " + url + " ]");
    this.logger.trace("Querystring: [ " + base.util.stringifyData(data) + " ]");
    this.logger.trace("Request header: [ " + JSON.stringify(header) + " ]");

    var par = this;
    callback.bind(this);

    this.spider.post(url, function(data, status, headers) {
        par.logger.trace("Page status: " + status);

        if(status !== 200) {
            par.logger.warn("The server returns an error status");
        }

        if(data === "1") {
            var s = true;
            var msg = "";
            par.cookies = headers["set-cookie"][0].substr(0, headers["set-cookie"][0].length - 7);

            par.logger.info("Logged in");
            var baseheader = { "cookie" : par.cookies, "content-length" : 0, "user-agent" : par.getUserAgent() };

            /**
             * Use fun.bind(par) to bind par as the "this" pointer for fun.
             * @refer https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind
             * @refer NODE.JS IRC CHANNEL: 13:07 < shama> xadillax: foo(a, b callback.bind(foo))
             *                             13:10 < olalonde> foo (a, b fn) { fn = fn.bind(this); …. }
             */
            if(callback !== undefined) callback.bind(par)(s, msg, baseheader);
        } else {
            par.logger.error("Failed while logging in: " + data);
            var baseheader = { "content-length" : 0, "user-agent" : par.getUserAgent() };
            if(callback !== undefined) callback.bind(par)(s, msg);
        }
    }, header, data, "utf8").on("error", function(e){
        par.logger.error("Failed while logging in: " + e.message);
    });
}