fs.writeFile in a promise, asynchronous-synchronous stuff

Question

I need some help with my code. I\'m new at Node.js and have a lot of trouble with it.

What I\'m trying to do:

1) Fetch a .txt with Amazon products (ASINs) ;<

Answer 1

For easy to use asynchronous convert all callback to promise use some library like "bluebird" .

      .then(function(results) {
                fs.writeFile(ASIN + '.json', JSON.stringify(results), function(err) {
                    if (err) {
                        console.log(err);
                    } else {
                        console.log("JSON saved");
                        return results;
                    }
                })


            }).catch(function(err) {
                console.log(err);
            });

Try solution with promise (bluebird)

var amazon = require('amazon-product-api');
var fs = require('fs');
var Promise = require('bluebird');

var client = amazon.createClient({
    awsId: "XXX",
    awsSecret: "XXX",
    awsTag: "888"
});


var array = fs.readFileSync('./test.txt').toString().split('\n');
Promise.map(array, function (ASIN) {
    client.itemLookup({
        domain: 'webservices.amazon.de',
        responseGroup: 'Large',
        idType: 'ASIN',
        itemId: ASIN
    }).then(function(results) {
        fs.writeFile(ASIN + '.json', JSON.stringify(results), function(err) {
            if (err) {
                console.log(err);
            } else {
                console.log("JSON saved");
                return results;
            }
        })
    }).catch(function(err) {
        console.log(err);
    });
});