Adding a reset to Cycle counter example

counter.js

const Cycle = require('@cycle/core');
const {makeDOMDriver, div, button, p} = require('@cycle/dom');
const {Observable} = require('rx');


function main(sources) {
  const decrement$ = sources.DOM
    .select('.decrement').events('click').map(ev => -1);

  const increment$ = sources.DOM
    .select('.increment').events('click').map(ev => +1);

  const reset$ = sources.DOM
    .select('.reset').events('click').map(ev => 0);

  const action$ = Observable.merge(decrement$, increment$);
  const count$ = action$.startWith(0).scan((x,y) => x+y);
  const value$ = Observable.merge(count$, reset$);

  const vtree$ = value$.map(count =>
    div([
      button('.decrement', 'Decrement'),
      button('.increment', 'Increment'),
      button('.reset', 'Reset'),
      p('Counter: ' + count)
    ])
  );
  return { DOM: vtree$ };
}

const sources = {
  DOM: makeDOMDriver('.app')
}

// Normally you need to call Cycle.run, but Tricycle handles that for you!
// If you want to try this out locally, just uncomment this code.
//
// Cycle.run(main, sources);