take(), takeLast(), first(), last(), those opreators all take number or no param. takeUtil and takeWhile will take Observalbe and function.

 

takeUntil(notifier: ): Stop when another observalbe happens

var foo = Rx.Observable.interval(1000);var btn = document.querySelector('#stop');var stop$ = Rx.Observable.fromEvent(btn, 'click');/*--0--1--2--3--4--5--6--7--...       takeUntil()--0--1--2--3--4|*/var bar = foo.takeUntil(stop$);bar.subscribe(  function (x) { console.log('next ' + x); },  function (err) { console.log('error ' + err); },  function () { console.log('done'); },);  /*"next 0""next 1""next 2""next 3""next 4""done"  */

 

 

takeWhile(predicate: function): Abort when it meets the predicate function.

var foo = Rx.Observable.interval(1000);/*--0--1--2--3--4--5--6--7--...       takeWhile(x => x < 3)--0--1--2--|*/var bar = foo.takeWhile((x)=>{             return x<3;                      });bar.subscribe(  function (x) { console.log('next ' + x); },  function (err) { console.log('error ' + err); },  function () { console.log('done'); },);  /*"next 0""next 1""next 2""done"  */