my first attempt at a web crawler in node... obviously I have no idea how to use asynchronicity

crawler.js

var http    = require("http");
var fs      = require("fs");
var crawler = require("simplecrawler");
var cheerio = require("cheerio");
var util    = require('util');
var exit    = require('exit');

var log = console.log.bind(console);
function str(a) {return util.inspect(a, false, null);}

var url = "https://gist.github.com/matthewmorrone1?page=3";

crawler.initialProtocol = "https";
crawler.maxDepth = 1;
var out = 0;

crawler.crawl(url, function(queueItem, responseBuffer, response){
    log(url);
    if(out === 1) {
        exit();
    }
    var $ = cheerio.load(responseBuffer);
    var links = $("a").map(function() {
        return [$(this).find("span strong").html(), +$(this).attr("href")];
    }).filter(function() {
        return this[0];
    });
    out++;
    fs.writeFile("out.txt", /*str(queueItem)+"\n\n"+*/Array.prototype.join.call(links, "\n")/*+"\n\n"+str(response)*/, function(err) {
        if(err) {
            log(err);
        } else {
            log("The file was saved!");
        }
    });
}, function(queueItem) {
    log("fail");
});