Mongo DB make connection outside of post? - node.js

Question

I am using MongoDB to insert a record into the database, every time the post method is called. I know I do not want to connect to the db inside of the post function every time, but this is giving me errors? How can I correct this?
var mongo = require('mongodb');
var url = 'mongodb://localhost:27017/Wedding'
var db = function() {
mongo.connect(url, function(err, db){
if (!err){
return db;
}
});
}
app.post('/rsvp', function (req, res) {
var item ={
name: req.body.name,
attending: req.body.attending,
};
insertItem(item);
res.sendFile(path.join(__dirname + '/confirm.html'));
})
function insertItem(item){
db.collection('rsvpList').insertOne(item, function(err, result){
assert.equal(null, err);
})
}
I am getting this error:
TypeError: Object function () {
mongo.connect(url, function(err, db){
if (!err){
return db;
}
});
} has no method 'collection'
at insertItem (C:\Users\A587092\Documents\weddingWebsite\server.js:53:8)
at app.listen.host (C:\Users\A587092\Documents\weddingWebsite\server.js:38:4)
at Layer.handle [as handle_request] (C:\Users\A587092\Documents\weddingWebsite\node_modules\express\lib\router\layer.js:95:5)

Answer 1

The problem is your db does not point to the Mongo instance rather to a function!
Try this -
var mongo = require('mongodb');
var url = 'mongodb://localhost:27017/Wedding'
var db;
mongo.connect(url, function(err, connectedDB){
if (!err){
db = connectedDB;
}
});

Answer 2

You couldn't simply return a value from an asynchronous method:
You should use a callback function:
var connectDb = function(url, cb) {
mongo.connect(url, function(err, db){
if ( err ) {
cb( err );
}
cb(null, db);
});
};
Usage:
function insertItem(item) {
connectDb(url, function(error, db) {
if ( error ) {
throw error;
}
db.collection('rsvpList').insertOne(item, function(err, result) {
assert.equal(null, err);
});
});
}
Or a promise:
var connectDb = function(url) {
return new Promise(function(resolve, reject) {
mongo.connect(url, function(err, db){
if ( err ) {
reject(err);
}
resolve(db);
});
});
};
Usage:
function insertItem(item) {
connectDb(url)
.then(function(db) {
db.collection('rsvpList').insertOne(item, function(err, result) {
assert.equal(null, err);
});
}, function(err) {
throw err;
});
}
I change the function name from db to connectDb because we want to connect to db and then doing something after connecting. and this way your code reads well.
Also note that here also your insertItem function doing an asynchronous task so if you need the result outside of this function you should implement a similar approach, i leave it to you ;)