How can I chain promises and multiple asynchronous requests?

Question

I'm requesting data from an api and then storing it to a database:

The database

MongoClient.connect(url, { useNewUrlParser: true }) .then((db)=>{ let dbo = db.db("scraper"); // This will be the api-response: dbo.collection("sold").insertOne( { item: "canvas", qty: 100, tags: ["cotton"], size: { h: 28, w: 35.5, uom: "cm" } } ) db.close(); }) .catch(err => { console.log(err) });

The api

fetch(link, {headers: {"Content-Type": "application/json; charset=utf-8"}}) .then(res => res.json()) // parse response as JSON (can be res.text() for plain response) .then(response => { console.log(util.inspect(response, {showHidden: false, depth: null, colors: true})); // This is where I'll be storing the data }) .catch(err => { console.log(err) });

I could just nest the fetch-response inside the MongoClient, but I would much rather start both requests and then, once they are both done, start a chain of promises. Is this possible?

Pedro Silva · Accepted Answer · 2018-11-10 17:24:41Z

If you want to start promises at the same time, you should try to use Promise.All.

Here is an example

var promise1 = Promise.resolve(3); var promise2 = 42; var promise3 = new Promise(function(resolve, reject) { setTimeout(resolve, 100, 'foo'); }); Promise.all([promise1, promise2, promise3]).then(function(values) { console.log(values); }); // expected output: Array [3, 42, "foo"]

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