The from() operator allows us to create an Observable from some other asynchronous/synchronous concept. It's really powerful when almost anything can be made into an Observable, as this allows for rich composition. Here is what a typical snippet can look like:
let stream$ = Rx.Observable.from(new Promise(resolve, reject) => { resolve('some data');});stream$.subscribe( data => console.log(data)); // some datalet stream2$ = Rx.Observable.from([1,2,3,4]);stream2$.subscribe( data => console.log(data)); // 1,2,3,4
