This is basically a duplicate of #42 so please read it first...
I think it has something to do with a 3 year old version of the ews-javascript-api. I tried using the latest version (0.10.0 instead of 0.8.0 used in this repo) but it seems like something has fundamentally changed in the newer version.
I have absolutely nothing to do with nodejs and can't fix it myself but if anyone wants to look into it, i'd send you a couple of original bavarian beers ;)