//take the first observable to emit

const example = Rx.Observable.race(

  //emit every 1.5s

  Rx.Observable.interval(1500),

  //emit every 1s

  Rx.Observable.interval(1000).mapTo('1s won!'),

  //emit every 2s

  Rx.Observable.interval(2000),

  //emit every 2.5s

  Rx.Observable.interval(2500)

);

//output: "1s won!"..."1s won!"...etc

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