take(), takeLast(), first(), last(), those opreators all take number or no param. takeUtil and takeWhile will take Observalbe and function.
takeUntil(notifier: Observable): 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"
*/