[xg15]

Last time I checked (~ a year ago admittedly), the node.js api itself (e.g. fs) was still mostly callback-based and had little built-in support for promises. You either had to resort to 3rd-party wrapper modules or wrap the calls yourself, resulting in a lot of clutter in your code.

Does anyone know if the situation has changed by now and you can obtain promises from core functions directly?

[Klathmon]

The situation is still that callbacks are king in the node core libraries. But there is some talk about how to move forward[0], however I don't think there has been much headway as of the last time I really looked into it about 6-months ago.

That being said, there are some fantastic libraries which you can use as a drop-in replacement for the core libraries provide a promise based API, but nothing in core directly.

[0] https://github.com/nodejs/NG/issues/25

[gotchange]

Can you recommend please some of these non CB based libraries?

[Klathmon]

The only one i've used before is Bluebird's `promisifyAll` method.

So when you require libraries, you can do so like:

    const fs = Promise.promisifyAll(require('fs'))
    // ... later    
    const fileContents = await fs.readFileAsync('filename.txt')

Basically it just adds "Async" after all functions that use node style callbacks.

[shawndellysse]

mz (https://www.npmjs.com/package/mz) is my go-to. You just prefix the core lib ("fs") with "mz/" ("mz/fs") and you get the promised version.

    const fs = require("fs");
    fs.exists(`${ __dirname }/1`, (exists1) => {
      fs.exists(`${ __dirname }/2`, (exists2) => {
        console.log(JSON.stringify([exists1, exists2]));
      });
    });

vs

    const fs = require("mz/fs");
    Promise.all([
      fs.exists(`${ __dirname }/1`),
      fs.exists(`${ __dirname }/2`),
    ])
    .then((existers) => {
      console.log(JSON.stringify(existers));
    });

Or

    const fs = require("mz/fs");
    (async () => {
      console.log(JSON.stringify(await Promise.all([
        fs.exists(`${ __dirname }/1`),
        fs.exists(`${ __dirname }/2`),
      ])));
    })();

[karmelapple]

supertest-as-promised is pretty great for testing purposes.

[mikewhy]

Regular supertest supports promises.