Node/Mongoose model creation executing before declaration assignment - node.js

Question

Facebook.create executes before fbUtils.getLongTermToken finishes retrieving the long term token. This is causing validation issues when trying to create the user. Do I need to use promises to manage the asynchronous execution that's happening here?
var userData = req.body;
userData.email = userData.email.toLowerCase();
userData.fbAuthToken = fbUtils.getLongTermToken(userData.fbAuthToken);
FacebookUser.create(userData, function (err, fbUser) {
console.log(userData.fbAuthToken);
if (err) {
console.log(err.message);
if (err.toString().indexOf('E11000') > -1) {
err = new Error('Email already exists.');
}
res.status(400);
return res.sendStatus({reason: err.toString()});
} else {
res.send('success');
}
});
Here's the code for fbUtils.getLongTermToken:
getLongTermToken: function (token) {
var options = {
host: 'graph.facebook.com',
path: '/oauth/access_token?grant_type=fb_exchange_token'
+ '&client_id=' + CONSTANTS.FACEBOOK_APP_ID
+ '&client_secret=' + CONSTANTS.FACEBOOK_APP_SECRET
+ '&fb_exchange_token=' + token
};
var str = '';
http.get(options, function (res) {
res.on('data', function (chunk) {
str += chunk;
});
res.on('end', function () {
console.log(str);
console.log(fbUtils.parseToken(str));
return fbUtils.parseToken(str);
});
}).on('error', function(err) {
console.log('longterm error: ' + err.message);
});
return str;
}

Answer 1

You need to update getLongTermToken to take a callback too, which will be called when the token retrieval is complete. For example:
getLongTermToken: function (token, cb) {
var options = {
host: 'graph.facebook.com',
path: '/oauth/access_token?grant_type=fb_exchange_token'
+ '&client_id=' + CONSTANTS.FACEBOOK_APP_ID
+ '&client_secret=' + CONSTANTS.FACEBOOK_APP_SECRET
+ '&fb_exchange_token=' + token
};
var str = '';
http.get(options, function (res) {
res.on('data', function (chunk) {
str += chunk;
});
res.on('end', function () {
console.log(str);
console.log(fbUtils.parseToken(str));
return cb(fbUtils.parseToken(str));
});
}).on('error', function(err) {
console.log('longterm error: ' + err.message);
});
}
Then you need to update your calling code to wait for this token:
var userData = req.body;
userData.email = userData.email.toLowerCase();
fbUtils.getLongTermToken(userData.fbAuthToken, function (token) {
userData.fbAuthToken = token;
FacebookUser.create(userData, function (err, fbUser) {
console.log(userData.fbAuthToken);
if (err) {
console.log(err.message);
if (err.toString().indexOf('E11000') > -1) {
err = new Error('Email already exists.');
}
res.status(400);
return res.sendStatus({reason: err.toString()});
} else {
res.send('success');
}
});
});

Answer 2

Because fbUtils.getLongTermToken is async, Facebook.create should be called in its callback, after the token is retrieved and parsed.
getLongTermToken: function (token) {
var options = {
host: 'graph.facebook.com',
path: '/oauth/access_token?grant_type=fb_exchange_token'
+ '&client_id=' + CONSTANTS.FACEBOOK_APP_ID
+ '&client_secret=' + CONSTANTS.FACEBOOK_APP_SECRET
+ '&fb_exchange_token=' + token
};
var str = '';
http.get(options, function (res) {
res.on('data', function (chunk) {
str += chunk;
});
res.on('end', function () {
console.log(str);
console.log(fbUtils.parseToken(str));
var parsedToken = fbUtils.parseToken(str);
// The earliest point where the token can be used
Facebook.create(...);
return parsedToken;
});
}).on('error', function(err) {
console.log('longterm error: ' + err.message);
});
return str;
}