You can use Ajax to request their user page, and in the json it should specify all of the groups they're in.
ah sorry forgot to reply here,
meantime I found out, that its not a problem in custom JS to use app.user.groupTitle 🙂
it works fine so good
Right now shared server providers using WHM/CPanel are finding it tough to integrate Node.js, as it is a standalone application (with its own bundled web server), unlike apps like wordpress/drupal, which are PHP based.
Until such a time as this is supported, you're going to have to install NodeBB on a virtual private server (i.e. Linode, Digital Ocean)