angular-docs-cn/modules/angular2/examples/facade/ts/async/observable_pure.ts

// #docregion Observable
import {Observable} from 'rxjs/Observable';
import {map} from 'rxjs/operator/map';

var obs = new Observable(obs => {
  var i = 0;
  setInterval(_ => obs.next(++i), 1000);
});
map.call(obs, i => `${i} seconds elapsed`).subscribe(msg => console.log(msg));
// #enddocregion