//emit every 5s

const source = Rx.Observable.interval(5000);

//emit every 1s

const secondSource = Rx.Observable.interval(1000);

const example = source

  .withLatestFrom(secondSource)

  .map(([first, second]) => {

    return `First Source (5s): ${first} Second Source (1s): ${second}`;

  });

/*

  "First Source (5s): 0 Second Source (1s): 4"

  "First Source (5s): 1 Second Source (1s): 9"

  "First Source (5s): 2 Second Source (1s): 14"

  ...

*/

const subscribe = example.subscribe(val => console.log(val));