chokidar RxJS 4.x

listen.js

const     Rx = require( 'rx' ),
    chokidar = require( 'chokidar' ),
  dirWatcher = chokidar.watch( '/tmp' ),
changedFiles = Rx.Observable.fromEvent( dirWatcher, 'change' ),
subscription = changedFiles.subscribe(
  function( filenamefullpath ) {
    console.log( filenamefullpath );
  },
  function( err ) {
    console.log( 'Error: ' + err );
  },
  function () {
    console.log( 'Completed' );
  });