I ran into this problem today, and finding no good solutions for it, I created a module to address it. I was inspired by @fbartho's snippet, but wanted to avoid overwriting the fs module.
The module I wrote is Filequeue, and you use it just like fs:
var Filequeue = require('filequeue');
var fq = new Filequeue(200); // max number of files to open at once
fq.readdir('/Users/xaver/Downloads/xaver/xxx/xxx/', function(err, files) {
if(err) {
throw err;
}
files.forEach(function(file) {
fq.readFile('/Users/xaver/Downloads/xaver/xxx/xxx/' + file, function(err, data) {
// do something here
}
});
});