Callbacks

Callbacks

ExpressJs

1. http://expressjs.com/
2. GetStated - > Hello World
3. npm init
4. callback.js
5. Postman

Callbacks

ExpressJs With mongoDb

1. http://expressjs.com/en/guide/database-integration.html#mongo

2. npm install mongodb --save

3. Criar banco de dados no MongoDB adicionar dados
4. Adicionar codigo Banco NetCoders e Collection Alunos
5.  

Promises

1. https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Promise

Promises

function connectMongoDB() {
    return new Promise(function (resolve, reject) {
        MongoClient.connect('mongodb://localhost:27017/netcoders', function (err, db) {
            if (err) reject(err)
            resolve(db)

        })
    })
}

Promises

function getCollectionList(db) {
    return new Promise(function (resolve, reject) {
        db.collection('alunos').find().toArray(function (err, result) {
            if (err) reject(err)
            resolve(result)
        })
    })
}

Promises

app.get('/', function (req, res) {

    connectMongoDB().then(function(db){
        return getCollectionList(db)
    })
    .then(function(result){
        res.send(result)
    })
    .catch(function(err){
        res.status(500).send(err)
    });

})

Generators

• https://github.com/tj/co

function* (){
    
    yield promise;
}

Generators

• npm install co --save

app.get('/', (req, res) => {
    co(function* () {
        try {

            let db = yield connectMongoDB();
            let result = yield getCollectionList(db);
            res.send(result)

        } catch (error) {
            console.log(error)
            res.status(500).send(error)
        }
    })


})

Async Await

• http://koajs.com/
• npm i koa --save

Async Await

const Koa = require('koa');
const app = new Koa();
const MongoClient = require('mongodb');
const co = require('co');


app.use(async function (ctx) {

    try {
        let db = await connectMongoDB();
        let result = await getCollectionList(db);
        ctx.body = result;
    } catch (error) {
        ctx.body = error;
    }

});