How can I scrape href attributes into an Array with trumpet?

I'm trying to get the href attributes with trumpet and keep stalling at the Object (...href attribute...) has no method 'push' error. Same thing happens when trying to use the createWriteStream. The docs for this method mention a second parameter like this elem.getAttribute(name, cb), but I have no idea what cb is. 

var file = "...path...";
var links = [];
var trumpet = require('trumpet');
var tr = trumpet();

tr.selectAll('.list_album', function(album) {
    album.getAttribute('href').push(links);
});

var fs = require('fs');
fs.createReadStream(file).pipe(tr);
console.log(links);

push is a method on Array and your links object is an Array so it seems to me what you want to do is:

tr.selectAll('.list_album', function(album) {
    album.getAttribute('href', function (value) {
        links.push(value);
    });
});

I'm not familiar with trumpet but I'd expect this to work.