code sequence in nodejs - node.js

Question

I am new to node.js and I thought I was beginning to understand asynchronous functions, but this code made me think that I did not understand it correctly anyway.
I am preparing for an insert to mongoDB with mongoose, and the object to insert is post. What made me wonder is that not always post.kunde or post.leverandor is set before the insert.
I thought that as long there is no asynchronous function, the code should execute line by line.
function create_post(account, dato, fakturanummer, bilag, bilagstype, supplier, customer,
descr, moms, amount, saldo, comId ) {
return new Promise(function(resolve, reject) {
var post = new Posteringer;
post.konto = account;
post.dato = dato;
post.fakturanummer = fakturanummer;
post.bilag = bilag;
post.bilagstype = bilagstype;
if (Object.keys(supplier).length) {
post.leverandor = supplier;
}
if (Object.keys(customer).length) {
post.kunde = customer;
}
post.tekst = descr;
post.moms = moms;
post.belob = amount;
post.saldo = saldo;
post.companyId = comId;
var promise = Accounts.findSingle(comId, account).exec();
promise.then(function(acc) {
post.navn = acc.Navn;
console.log(post);
post.save(function(err) {
if (err) {console.log(err.message);}
resolve(true);
});
});
});
}

Answer 1

So there are a few things wrong here. A promise is basically saying "hey, I'm not done doing my stuff yet, but I'll promise to get this to you when I figure out all the things I need to do."
I am not entirely sure how you are calling this, but think of this like a big callback function. So after this you'd have something like,
create_post(......).then(
function(post){
post.save(function(err){
if (err) {console.log(err.message);}
});
});
The real issue I see is you are only resolving one promise. I am not 100% sure if you have to resolve the Mongo promise, unless you are using bluebird promises with it. Your first promise never gets returned though.
I will redo your code, I think this should work:
function create_post(account, dato, fakturanummer, bilag, bilagstype, supplier, customer,
descr, moms, amount, saldo, comId ) {
return new Promise(function(resolve, reject) {
var post = new Posteringer;
post.konto = account;
post.dato = dato;
post.fakturanummer = fakturanummer;
post.bilag = bilag;
post.bilagstype = bilagstype;
if (Object.keys(supplier).length) {
post.leverandor = supplier;
}
if (Object.keys(customer).length) {
post.kunde = customer;
}
post.tekst = descr;
post.moms = moms;
post.belob = amount;
post.saldo = saldo;
post.companyId = comId;
var promise = Accounts.findSingle(comId, account).exec();
promise.then(function(acc) {
post.navn = acc.Navn;
console.log(post);
});
return (err ? reject(err) : resolve(post));
});
}
Then when you call this function call it like in my first example!
create_post(......).then(
function(post){
post.save(function(err){
if (err) {console.log(err.message);}
});
});
Literally what you are saying is if this resolves and I get my data without any errors, send back post. Then pass post into my callback function and do whatever you want to do with it.
Edit:
Make sure you always return something from your promises, as far as I know the async call will never resolve as it never receives anything. Although someone might have an example where this isn't true.