How come a globally defined array that gets data pushed to it with in a callback function is empty in the global scope?

How come a globally defined array that gets data pushed to it with in a
callback function is empty in the global scope?

I assign an empty array to the global variable artistURLs. I then push
strings (the local variable artistURL) into the artistURLs array with in
the Cheerio .each() iterator method.
var request = require('request'),
cheerio = require('cheerio'),
url = 'http://www.primarytalent.com/',
artistURLs = [];
request(url, function(err, resp, body){
if(err)
throw err;
$ = cheerio.load(body);
$('#rosterlists div li a').each(function(){
var urlCap = this.attr('href').slice(1);
var artistURL = url.concat(urlCap);
artistURLs.push(artistURL);
});
console.log(artistURLs);
});
I know that artistURL is successfully being pushed into artistURLs because
console.log(artistURLs);
will display the populated array in my terminal. The problem is if I try
running console.log(artistURLs); outside of the callback function in the
global scope. For example
var request = require('request'),
cheerio = require('cheerio'),
url = 'http://www.primarytalent.com/',
artistURLs = [];
request(url, function(err, resp, body){
if(err)
throw err;
$ = cheerio.load(body);
$('#rosterlists div li a').each(function(){
var urlCap = this.attr('href').slice(1);
var artistURL = url.concat(urlCap);
artistURLs.push(artistURL);
});
});
console.log(artistURLs);
So you can see that I have moved console.log(artistURLs); outside of
request(). For some reason trying to access artistURLs in the global scope
returns me an empty array as if all the processing that happened with in
`request()~ never even happened.
How come this is happening and how can ensure that all the urls that are
being pushed into artistURLs remain in artistURLs?
Thanks