Dealing with asynchronous functions. Custom callback? - node.js

Question

I have the code below and am trying to access the all_records array once the _.each function has completed. However as it is asynchronous I was wondering if was possible to force a callback onto the underscores each?
var request = require('request'),
cheerio = require('cheerio'),
_ = require('underscore');
var all_records = [];
_.each([0,100], function(start) {
var base_url = "http://www.example.com/search?limit=100&q=foobar&start=";
var url = base_url + start;
request(url, function(err, res, body) {
var $ = cheerio.load(body),
links = $('#results .row');
$(links).each(function(i, link) {
var $link = $(link);
var record = {
title: $link.children('.title').text().trim()
};
all_records.push(record);
});
});
});
// Need to run this once _.each has completed final iteration.
console.log(all_records);

Answer 1

Here is a simple solution using a simple synchronization method:
var count = 101;//there are 101 numbers between 0 and 100 including 0 and 100
_.each([0,100], function(start) {
var base_url = "http://www.example.com/search?limit=100&q=foobar&start=";
var url = base_url + start;
request(url, function(err, res, body) {
var $ = cheerio.load(body),
links = $('#results .row');
$(links).each(function(i, link) {
var $link = $(link);
var record = {
title: $link.children('.title').text().trim()
};
all_records.push(record);
count--;
if(count===0){//101 iterations done
console.log(all_records);
}
});
});
});
A more elegant solution can be accomplied by using async's .parallel method.
var requests = []; //an array for all the requests we will be making
for(var i=0;i<=100;i++){
requests.push((function(done){ //create all the requests
//here you put the code for a single request.
//After the push to all_records you make a single done() call
//to let async know the function completed
}).bind(null,i));//the bind is that so each function gets its own value of i
}
async.parallel(requests,function(){
console.log(all_records);
});

Answer 2

async.each ended up being the easiest to implement.
async.each([0,100], function(start) {
var base_url = "http://www.example.com/search?limit=100&q=foobar&start=";
var url = base_url + start;
request(url, function(err, res, body) {
var $ = cheerio.load(body),
links = $('#results .row');
$(links).each(function(i, link) {
var $link = $(link);
var record = {
title: $link.children('.title').text().trim()
};
all_records.push(record);
});
});
}, function(err){
console.log(all_records);
});