const source = Rx.Observable.from([1,2,3,4,5]);

var single = source.single( x => x === 3);

/*

(12345)|                   (source)

single( x => x === 3)

3|                         (single)

*/

var sub = single.subscribe( x =>  console.log(x)); //

const winner = 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)

).take(1);

/**

------0                 (1500)

----0                   (1000).mapTo('1s won!')

--------0               (2000)

----------0             (2500)

race

----(1s won!)|          (take(1))

*/

const sub2 = winner.subscribe( x => console.log(x)); // 1s won!