Steaming from mouse Events

var refreshClickStream = Rx.Observable.fromEvent(refreshButton, 'click');

The above will create a click event stream.

The code below will map that click stream into a subscribableurl stream, meaning every subscribable click will map to a subscribable URL request stream. 
The click stream will contain all clicks, and all clicks are mapped to url values.

var requestStream = refreshClickStream

  .map(function() {

    var randomOffset = Math.floor(Math.random()*500);

    return 'https://api.github.com/users?since=' + randomOffset;

  });

Merging streams
Lets say you have a stream for click url requests (as we did previously), and a stream for the startup url requests, which is subscribed to seperatly.
The  stream for the startup url requests looks as follows:

var startupRequestStream = Rx.Observable.just('https://api.github.com/users');

And lets say you want to subscribe to both the click url requests & the seperate startupRequestStream , and log all requests into the console, regardless of which request was made.
One way to achieve that is to pass the same functions to both subscription, where the console function will be called.
The correct way is to merge both subscriptions into a single stream (observable) of both of the url subscription (startupRequestStream  & refreshClickStream).
Example:

var requestStream = Rx.Observable.merge(

  refreshClickStream, startupRequestStream

);

Now we have a single stream that will emit on both the refreshClickStream & startupRequestStream Observables.