doesn't work with nodejs

[RichardWright]

Running this within nodejs fails with this error

return rxjs_1.fromEvent(document, 'visibilitychange').pipe(operators_1.startWith(null), operators_1.switchMap(function () { ReferenceError: document is not defined at polling (/Users/83592/projects/metrics-emitter/node_modules/rx-polling/lib/index.js:27:29)

Will this always be a client side library?