/**

​

Countdown Exercise

​

Lesson:

    interval(1000) creates a stream that emits incremental numbers every 1000ms. 

    - 1000ms after the stream has started, it emits 0

    - Then, after 1000ms it emits 1

    - And so on

​

Exercise: 

    - Create a countdown from 10 to 0

    - The stream starts immediately with 10 (you shouldn't see the '?' default document value)

    - The stream completes immediately after 0

Hints: 

    - Begin with Rx.Observable.interval(1000)

    - Complete with some operators from http://reactive.how/categories

Test: 

     - Watch the result on the "Output" panel, as you type

     - Click "Run with JS" above this panel to reset the execution

*/

​

const countdown =

      Rx.Observable   

        .interval(1000)

        //map(n=>n+1)

countdown.subscribe(n => document.body.innerHTML = n);