I wanna use promises for mongodb in NodeJS. So, I had some code:
const mongo = require('mongodb').MongoClient;
const config = require('./config.json');
mongo.connect(config.URI, function (err, client) {
const db = client.db("INDFLORIST");
const collection = db.collection('API');
collection.insertOne({name: 'Roger'}, function (err, res) {
if (err) throw err;
console.log("Document inserted");
client.close();
});
});
Then I've convert callback
to promise
:
const mongo = require('mongodb').MongoClient;
const config = require('./config.json');
mongo.connect(config.URI).then(client => {
const db = client.db("INDFLORIST");
const collection = db.collection('API');
return collection.insertOne({name: 'Roger'});
})
.then(function(result) {
console.log("Document inserted");
}).then(client => {
client.close();
})
.catch(err => {
console.error(err);
});
But this script invoke error: TypeError: Cannot read property 'close' of undefined.
Can u help me? How solve this problem?
You can create some external variable _client_
and after successful connection assign client
to it, then you can use _client_
to close connection in last then
callback
const mongo = require("mongodb").MongoClient;
const config = require("./config.json");
let _client_; // <-- external variable
mongo.connect(config.URI).then(client => {
_client_ = client; // <-- assing real client to it
const db = client.db("INDFLORIST");
const collection = db.collection("API");
return collection.insertOne({name: "Roger"});
}).then(function (result) {
console.log("Document inserted");
}).then(() => {
_client_.close(); // <-- close connection
}).catch(err => {
console.error(err);
});
You can also pass it thru all then
callbacks
const mongo = require("mongodb").MongoClient;
const config = require("./config.json");
mongo.connect(config.URI).then(client => {
const db = client.db("INDFLORIST");
const collection = db.collection("API");
return collection.insertOne({name: "Roger"}).then(() => client);
}).then(function (client) {
console.log("Document inserted");
return client;
}).then(client => {
client.close();
}).catch(err => {
console.error(err);
});