MeteorJS: CALLBACKS - meteor

Question

PROBLEM: I want to parse the elements in a page from another website, glue resulting elements in an object and insert it in a Mongo collection. Before insertion i want to check if my Mongo yet has an identical object. If it does it shall exit the running functions, otherwise i want the script to start parsing the next target.
Example:
I have a function that connects to a webpage and returns its body content
It is parsed
When <a></a> elements are met, another callback is called in which all parsed elements are merged in one object and inserted in a collection
My code :
var Cheerio = Meteor.npmRequire('cheerio');
var lastUrl;
var exit = false;
Meteor.methods({
parsing:function(){
this.unblock();
request("https://example.com/", Meteor.bindEnvironment(function(error, response, body) {
if (!error && response.statusCode == 200) {
$ = Cheerio.load(body);
var k = 1;
$("div.content").each(function() {
var name = $...//parsing
var age = $....//parsing
var url = $...//parsing <a></a> elements
var r = request("https://example.com/"+url, Meteor.bindEnvironment(function(error, response, body) {
lastUrl = response.request.uri.href;// get the last routing link
var metadata = {
name: name,
age: age
url: lastUrl
};
var postExist;
postExist = Posts.findOne(metadata); // return undefined if doesnt exist, AND every time postExist = undefined ??
if (!postExist){
Posts.insert(metadata);// if post doesnt exist (every time go here ??)
}
else {
exit = true; // if exist
}
}));
if (exit === true) return false;
});
}
}));
}
});
Problem 1 : The problem is my function works every time, but it doesn't stop even if the object exists in my collection
Problem 2 : postExist is always undefined
EDIT : The execution must stop and wait until the second request's response.
var url = $...//parsing <a></a> elements
//STOP HERE AND WAIT !!
var r = request("https://example.com/"+url, Meteor.bindEnvironment(function(error, response, body) {

Answer 1

Looks like you want the second request to be synchronous and not asynchronous.
To achieve this, use a future
var Cheerio = Meteor.npmRequire('cheerio');
var Future = Meteor.npmRequire('fibers/future');
var lastUrl;
var exit = false;
Meteor.methods({
parsing:function(){
this.unblock();
request("https://example.com/", Meteor.bindEnvironment(function(error, response, body) {
if (!error && response.statusCode == 200) {
$ = Cheerio.load(body);
var k = 1;
$("div.content").each(function() {
var name = $...//parsing
var age = $....//parsing
var url = $...//parsing <a></a> elements
var fut = new Future();
var r = request("https://example.com/"+url, Meteor.bindEnvironment(function(error, response, body) {
lastUrl = response.request.uri.href;// get the last routing link
var metadata = {
name: name,
age: age
url: lastUrl
};
var postExist;
postExist = Posts.findOne(metadata); // return undefined if doesnt exist
if (!postExist) {
Posts.insert(metadata);// if post doesnt exist (every time go here ??)
fut.return(true);
} else {
fut.return(false);
}
}));
var status = fut.wait();
return status;
});
}
}));
}
});
You can use futures whenever you can't utilize callback functions (e.g. you want the user to wait on the result of a callback before presenting info).
Hopefully that helps,
Elliott

Answer 2

This is the opposite :
postExist = Posts.findOne(metadata); // return undefined if doesnt exist > you're right
if (!postExist){ //=if NOT undefined = if it EXISTS !
Posts.insert(metadata);
}else {
exit = true; // if undefined > if it DOES NOT EXIST !
}
You need to inverse the condition or the code inside