Output looped PIWIK API call to CSV - node.js

Question

I've got the following problem: I am looping through API calls using different dates to append the output to a CSV file. However, the output data in the CSV file only contains data from the first date.
When I log the results to the command prompt I do get multiple dates, meaning the problem occurs when writing the output to the CSV.
Moment.js is used for setting the start and end date to loop through and fast-csv to write the output of the API call to a CSV file.
// load and configure
const piwik = require ('piwik').setup ('placeholderurl', 'XXXXX');
// filesystem requirement
var fs = require('fs');
// fast-csv requirement
var csv = require("fast-csv");
// moment.js requirement
var moment = require('moment');
// variabelen voor het loopen door datums
var a = moment().format('2016-05-12');
var b = moment().format('2016-05-15');
var stream = fs.createWriteStream ('my.csv', {flags: 'a'})
// samenstellen API url
for (var m = moment(a); m.isBefore(b); m.add(1, 'days')) {
piwik.api (
{
method: 'Live.getLastVisitsDetails',
idSite: 3,
period: 'day',
format: 'csv',
date: moment(m).format('YYYY-MM-DD')
},
function (err, data) {
if (err) {
console.log (err);
return;
}
console.log(data)
csv
.writeToStream(fs.createWriteStream("my.csv"), data, {flags: 'a', headers: true});
}
);
}
API token and url removed for privacy reasons.

Answer 1

Solved. Got rid of the PIWIK API package and decided to use HTTP GET to retrieve the url manually.
The code:
// http requirement
var http = require('http');
var request = require('request');
// filesystem requirement
var fs = require('fs');
// moment.js requirement
var moment = require('moment');
// variabelen voor het loopen door datums
var a = moment().format('2016-05-12');
var b = moment().format('2016-05-15');
var m = moment(a);
//var stream = fs.createWriteStream ('my.csv', {flags: 'a'})
// samenstellen API url
for (var m = moment(a); m.isBefore(b); m.add(1, 'days')) {
request
.get("http://placeholder.com/?module=API&method=Live.getLastVisitsDetails&idSite=3&period=day&date=" + moment(m).format('YYYY-MM-DD') + "&format=csv&token_auth=placeholdertoken&filter_limit=-1")
.on('error', function(err) {
console.log(err)
})
.pipe(fs.createWriteStream('data-' + moment(m).format('YYYY-MM-DD') + '.csv'))
console.log(moment(m).format('YYYY-MM-DD') + " " + "saved")
}