Issue with Promise - promise

Question

I got a small problem with my function below. The Promise.map doesn't wait for Folder.create to be finished and iterate through the next value.
Promise.map(name, function(na){
return fs.stat(na.url, function(err, stats){
if (typeof stats === 'undefined'){
console.log("file doesn't exist");
return Folder.create(na).then(function(fd){
return mkdirp(root + product.url).then(function(){
console.log("Folder Created");
return null;
});
}, function(err){
console.log(err);
return reject({message: "Error when creating the folder"});
});
}
});
}).then(function(){
console.log('Iteration Done');
return resolve({message: "Folder Created!"});
});
// I GOT :
//file doesn't exist
//file doesn't exist
//file doesn't exist
//Iteration Done
//file doesn't exist
//file doesn't exist
//file doesn't exist
//Iteration Done
//Folder Created
//Folder Created
//Folder Created
//Folder Created
//Folder Created
//Folder Created

Answer 1

There are a couple issues here:
Promise.map() runs the operations for each array element in parallel, not serially. If you want them run serially, you can pass {concurrency: 1} as an option to Promise.map() or use Promise.mapSeries().
fs.stat() does not return a promise so your main callback to Promise.map() isn't returning a promise so the whole Promise.map() infrastructure does not know how to wait for any of your results. You can promisify fs.stat() to solve that issue.
You appear to be using an anti-pattern with your resolve() and reject() calls in here. You don't show the outer definition where those come from, but you should be just using the promise returned from Promise.map() rather than doing that.
Here's how they can successfully be run in parallel:
var fs = Promise.promisifyAll(require('fs'));
Promise.map(name, function(na){
return fs.statAsync(na.url).then(function(err, stats){
if (typeof stats === 'undefined'){
console.log("file doesn't exist");
return Folder.create(na).then(function(fd){
return mkdirp(root + product.url).then(function(){
console.log("Folder Created");
return null;
});
}, function(err){
console.log(err);
return Promise.reject({message: "Error when creating the folder"});
});
}
});
}).then(function(){
console.log('Iteration Done');
return ({message: "Folder Created!"});
});
If you wanted to run your operations serially with Bluebird, you could pass {concurrency: 1} to Promise.map():
Promise.map(name, fn, {concurrency: 1}).then(...);
Or use:
Promise.mapSeries(name, fn).then(...)

Answer 2

fs.stat is a callback type function and thus, does not return a Promise. You should modify your code to be something like this
// This might not work directly. I haven't tried to run it
Promise.map(name, function(na) {
return new Promise(function(resolve, reject) {
fs.stat(na.url, function(err, stats) {
if (typeof stats === 'undefined') {
console.log("file doesn't exist");
Folder.create(na).then(function(fd) {
return mkdirp(root + product.url);
}).then(function() {
console.log("Folder Created");
resolve();
}).catch(function(err) {
console.log(err);
reject({
message: "Error when creating the folder"
});
});
} else {
resolve();
}
});
});
}).then(function() {
console.log('Iteration Done');
return {
message: "Folder Created!"
};
});