[RxJS] Filtering operators: take, first, skip

There are more operators in the filtering category besides filter(). This lesson will teach how take(), first(), and skip() are simply operators to ignore or pass a certain amount of events from the source Observable.

 take(number):

var foo = Rx.Observable.interval(100);

/*
--0--1--2--3--4--5--6--7-
         take(5)
--0--1--2--3--4
*/

var bar = foo.take(5);

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"
  */

first():

var foo = Rx.Observable.interval(100);

/*
--0--1--2--3--4--5--6--7-
         first()
--0
*/

var bar = foo.first();

bar.subscribe(
  function (x) { console.log('next ' + x); },
  function (err) { console.log('error ' + err); },
  function () { console.log('done'); },
);

  /**
  "next 0"
"done"
  */

skip(number): different with take(), it skip the first number of item, and show the rest:

var foo = Rx.Observable.interval(100);

/*
--0--1--2--3--4--5--6--7
    skip(5).take(3)
-----------------5--6--7
*/

var bar = foo.skip(5).take(3);

bar.subscribe(
  function (x) { console.log('next ' + x); },
  function (err) { console.log('error ' + err); },
  function () { console.log('done'); },
);

  /**
  "next 5"
"next 6"
"next 7"
"done"
  */