How to insert data from async call into push method

Question

I am user of https://github.com/jackspirou/clientjs. It creates fingerprint of user visiting my site. I am also user of Piwik, open source analytic tool. I'm trying to implement one of its feature - http://developer.piwik.org/guides/tracking-javascript-guide#user-id.

My code looks like:

var client = new ClientJS();
var fingerprint = client.getFingerprint();

var _paq = _paq || [];
_paq.push(['setUserId', fingerprint]);
_paq.push(['trackPageView']);

And it does not work. Data inserted by code above into my database are "NULL" for UserID field. It is probably the problem with getFingerprint() being asynchronous. My question is - how to bypass it?

Answer 1

You have to look at the client.getFingerprint() documentation. Most likely it's something like this:

client.getFingerprint(function(result, err) {
    // check for err
    // do something with result
    var _paq = _paq || [];
    _paq.push(['setUserId', result]);
    _paq.push(['trackPageView']);
});

Note, I'm only guessing the returning data as result and err, but it could be on object. Also, I'm guessing it accepts the callback function as one single parameter.