rnjs

RN

Reactive Programming Library for TypeScript

glitch-less & hot Observable only RxJS

Usage

• installation

npm install rxjs rnjs

• import

import { RN, interval } from 'rnjs'

const a: RN<number> = interval(1000, true);  // generate RN

a.subscribe( console.log );

// 0
// 1
// 2
// ...

features

• glitch-less

  • in RxJS

      const a = interval(1000);
      const b = a.pipe( map( x => 100 * x ) );
      const c = combineLatest( a, b ).pipe( map( ([x, y]) => x + y ) );
      c.subscribe( console.log );
      // 0
      // 1  <-- glitch
      // 101
      // 102  <-- glitch
      // 202
      // 203  <-- glitch
      // 303
      // 304  <-- glitch
      // 404
      // 405  <-- glitch
      // 505
      // ...
  

  • in RN

      // RN
      const a = interval(1000, true);
      const b = a.map( x => 100 * x );
      const c = combine( a, b ).map( ([x, y]) => x + y );
      c.listen( true, console.log );
  
      // 0
      // 101
      // 202
      // 303
      // 404
      // 505
      // ...
  

  • about "glitch"
    • RX GLITCHES AREN'T ACTUALLY A PROBLEM
    • Bainomugisha, Engineer, et al. "A survey on reactive programming." ACM Computing Surveys (CSUR) 45.4 (2013): 52.
  • all tasks are processed by the priority-queue

• initial value

  • all RNs have initial values
  • you can get the current value with value property (like BehaviorSubject in RxJS)

      import { RN, interval } from 'rnjs'
  
      const a: RN<number> = interval(1000, true).take(8);
  
      a.subscribe( console.log );
  
      // |0---1---2---3---4---5---6---7---|
      //                ^
      setTimeout( () => console.log( a.value ), 3500 );  // 3
  
      // |0---1---2---3---4---5---6---7---|
      //                        ^
      setTimeout( () => console.log( a.value ), 5500 );  // 5
  

• hot-RN(Observable) only

  • no cold/hot conversion is necessary
  • all subscribers of the RN receive the same value at the same time

• compatiblity with RxJS

  • mutual conversion methods (toObservable, fromObservable)
  • the same subscribe API as RxJS
    • RN can be passed to Angular async pipe without conversion to RxJS Observable

Coresspondence tables to RxJS

• Source RNs

RN	RxJS v6
interval	interval
fromEvent	fromEvent
fromPromise	from
fromObservable	-
manual	BehaviorSubject
-	...

• Combination methods

RN	RxJS v6
combine	combineLatest
merge	merge
-	concat
-	zip
-	...

• Operators

RN	RxJS v6
auditTime	auditTime
delay	delay
debounce	debounceTime
filter	filter
flatMap	flatMap
map	map
mapTo	mapTo
pairwise	pairwise
pluck	pluck
scan	scan
skip	skip
skipAlreadyAppeared	distinct
skipUnchanged	distinctUntilChanged
skipWhile	skipWhile
startWith	startWith
switchMap	switchMap
take	take
takeWhile	takeWhile
throttle	throttle
withLatest	withLatestFrom
withTimestamp	timestamp
withInitialValue	-
-	...

Examples

• interval, combine, map

import { interval, combine, map } from 'rnjs';

const a = interval(100, true);
                       // ^
                       // +--- true --> start immediately
const b = a.pipe( map( x => 100 * x ) );
const c = combine( a, b ).map( ([x, y]) => x + y );
c.subscribe( console.log );
// c.listen( true, console.log );

/* output
0
101
202
303
404
505
...
*/

import { interval, combine } from 'rnjs';

const a = interval(100, false);
                        // ^
                        // +--- false --> start manually
const b = a.map( x => 100 * x );
          // ^
          // +--- all operators can be used without pipe method
const c = combine( a, b ).map( ([x, y]) => x + y );
c.listen( true, console.log );
          // ^
          // +--- true --> get the first value
a.start();  // start manually

/* output
0  <-- first value
0
101
202
303
404
505
...
*/

• map (with index)
  • index is initialized by
  • map function receives
    • source RN value
    • source RN index (optional)
    • this.index (optional)
  • in the next example, a starts before b is generated --> a.index is not equal to b.index.

const a = interval(100, true);
const b = a.map( (sv, si, i) => [100 * sv, si, i] );
b.listen( true, console.log );

/*
[ 0, 0, -1 ]
[ 100, 1, 0 ]
[ 200, 2, 1 ]
[ 300, 3, 2 ]
[ 400, 4, 3 ]
[ 500, 5, 4 ]
[ 600, 6, 5 ]
[ 700, 7, 6 ]
[ 800, 8, 7 ]
[ 900, 9, 8 ]
*/

• withInitialValue

const a = interval( 100, false );
const b = a.withInitialValue(999)
b.listen( true, console.log );
a.start();

/*
999
0
1
2
3
4
5
6
7
...
*/

/*
interval         : 0   |0---1---2---3---4---5---6---7---8---9--
withInitialValue : 999 |0---1---2---3---4---5---6---7---8---9--
*/

• delay

const a = interval( 100, false );
const b = a.delay( 50 ).map( x => 100 * x );
const c = merge( a, b );
c.listen( false, console.log );
a.start();

/*
0
0
1
100
2
200
3
300
4
400
5
500
6
600
7
700
*/

/*
interval : 0 |0---1---2---3---4---5---6---7---8---9--
delay    : 0 |--0---1---2---3---4---5---6---7---8---9
*/

• debounce, filter

import { interval } from 'rnjs';

const a = interval(100, true);
const b = a.filter( 0, e => e % 10 < 5 );
                //  ^
                //  +--- filter requires initial value
const c = b.debounce(300);
b.listen( false, console.log );
c.listen( false, e => console.log( e, 'debounce') );

/* output
1
2
3
4
4 'debounce'
10
11
12
13
14
14 'debounce'
...
*/


/*
interval : 0 |0--1--2--3--4--5--6--7--8--9--10-11-12-13-14-15-16-17-18-19-
filter   : 0 |0--1--2--3--4-----------------10-11-12-13-14----------------
debounce : 0 |---------------------4-----------------------------14-------
*/

• throttle

const a = interval( 100, false );
const b = a.filter( 0, x => x % 10 < 5 ).throttle( 250 );
b.listen( false, console.log );
a.start();

/*
0
3
10
13
20
23
30
33
40
43
...
*/

/*
interval : 0 |0--1--2--3--4--5--6--7--8--9--10-11-12-13-14-15-16-17-18-19-
filter   : 0 |0--1--2--3--4-----------------10-11-12-13-14----------------
throttle : 0 |0--------3--------------------10-------13-------------------
*/

• scan

import { interval } from 'rnjs';

const a = interval(100, true);
const b = a.scan( [] as number[], (prev, curr) => {
  prev.push( curr );
  return prev;
});
a.listen( true, e => console.log('a', e ) );
b.listen( true, e => console.log('b', e ) );

/* output
a 0
b []
a 1
b [ 1 ]
a 2
b [ 1, 2 ]
a 3
b [ 1, 2, 3 ]
*/

• merge

import { interval, merge } from 'rnjs';

const a = interval(1000, false);
const b = interval(1000, false);
const c = b.map( e => 100 * e );
const d = merge( a, c );
a.start();
setTimeout(() => { b.start(); }, 500);
d.listen( true, console.log );

/* output
0
0
1
100
2
200
3
300
4
400
5
500
*/

/*
a : 0 |0-------1-------2-------3-------4-------5-------6-------
b : 0     |0------100-----200-----300-----400-----500-----600-----
c : 0 |0---0---1--100--2--200--3--300--4--400--5--500--6--600--
*/

• pairwise

import { interval } from 'rnjs';

interval(100, true).pairwise()
  .listen( true, console.log );

/* output
[ 0, 0 ]
[ 0, 1 ]
[ 1, 2 ]
[ 2, 3 ]
[ 3, 4 ]
[ 4, 5 ]
[ 5, 6 ]
[ 6, 7 ]
[ 7, 8 ]
...
*/

/*
interval : 0     |0------1------2------3------4------5------6------
pairwise : [0,0] |[0,0]--[0,1]--[1,2]--[2,3]--[3,4]--[4,5]--[5,6]--
*/

• pluck

import { interval } from 'rnjs';

const a = interval(100, true);
const b = a.pairwise()
            .map( e => ({ prev: e[0], curr: e[1] }) )
            .pluck('curr');
b.listen( true, console.log );

/* output
0
1
2
3
...
*/

• take

const a = interval(100, true);
const b = a.take(5);
b.listen( true, console.log );

/*
0
1
2
3
4
*/

• skip

const a = interval(100, true);
const b = a.skip( 999, 3 );
                // ^
                // +--- skip requires initial value
b.listen( true, console.log );

/*
999
3
4
5
6
7
8
9
*/

/*
interval : 0   |0---1---2---3---4---5---6---7---8---9---10--11--12--...
skip     : 999   |----------3---1---4---1---5---9---2---6---u---u---...
*/

• takeWhile, skipAlreadyAppeared

import { interval } from 'rnjs';

const values = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9];
const a = interval(100, false);
const b = a.map( (_sv, _si, i) => values[i] )
            .takeWhile( (_sv, _si, i) => 0 <= i && i < values.length )
            .skipAlreadyAppeared();
b.listen( false, console.log );
a.start();

/* output
3
1
4
5
9
2
6
8
*/

/*
interval            : 0 |0---1---2---3---4---5---6---7---8---9---10--11--12--13--14--...
map                 : 3 |3---1---4---1---5---9---2---6---5---3---5---8---9---u---u---
takeWhile           : 3 |3---1---4---1---5---9---2---6---5---3---5---8---9---
skipAlreadyAppeared : 3 |3---1---4-------5---9---2---6---------------8-------
*/

const values = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9];
const a = interval(100, true);
const b = a.map( (_sv, _si, i) => values[i] )
            .takeWhile( (_sv, _si, i) => 0 <= i && i < values.length )
            .skipAlreadyAppeared();
b.listen( false, console.log );

/* output
3
1
4
5
9
2
6
8
*/

/*
interval            : 0 |0---1---2---3---4---5---6---7---8---9---10--11--12--13--14--...
map                 : ud    |3---1---4---1---5---9---2---6---5---3---5---8---9---u---u---
takeWhile           : ud    |3---1---4---1---5---9---2---6---5---3---5---8---9---
skipAlreadyAppeared : ud    |3---1---4-------5---9---2---6---------------8-------
*/

• skipUnchanged

const values = [3, 3, 3, 1, 4, 1, 5, 9, 9, 9, 2, 6];
const a = interval(100, true);
const b = a.map( (_sv, _si, i) => values[i] )
            .takeWhile( (_sv, _si, i) => 0 <= i && i < values.length )
            .skipUnchanged();
b.listen( false, console.log );

/*
3
1
4
1
5
9
2
6
*/

/*
interval            : 0  |0---1---2---3---4---5---6---7---8---9---10--11--12--...
map                 : ud   |--3---3---3---1---4---1---5---9---2---6---u---u---...
takeWhile           : ud   |--3---3---3---1---4---1---5---9---2---6---
skipUnchanged       : ud   |--3-----------1---4---1---5---9---2---6---
*/

• withLatest

const a = interval(300, true);
const b = interval(100, true);
const c = a.withLatest( b );
c.listen( true, console.log );
/*
[ 0, 0 ]
[ 1, 2 ]
[ 2, 5 ]
[ 3, 8 ]
[ 4, 11 ]
[ 5, 14 ]
[ 6, 17 ]
[ 7, 20 ]
[ 8, 23 ]
[ 9, 26 ]
[ 10, 29 ]
*/

/*
a : 0     |0-----------1-----------2-----------3-----------4----...
b : 0      |0---1---2---3---4---5---6---7---8---9---10--11--12--...
c : [0,0]   |----------[1,2]-------[2,5]-------[3,8]-------[4,11]--...
*/

• withTimestamp

const a = interval(300, true);
const b = a.withTimestamp();
b.listen( true, console.log );

/*
[ 0, 1544903873595 ]
[ 1, 1544903873896 ]
[ 2, 1544903874195 ]
[ 3, 1544903874497 ]
[ 4, 1544903874797 ]
*/

• valueIs, valueIsNot

const a = interval( 500, true );
const b = a.valueIs(3);
combine(a, b).listen( true, console.log )

/*
[ 0, false ]
[ 1, false ]
[ 2, false ]
[ 3, true ]
[ 4, false ]
[ 5, false ]
...
*/

const a = interval( 500, true );
const b = a.valueIsNot(3);
combine(a, b).listen( true, console.log )

/*
[ 0, true ]
[ 1, true ]
[ 2, true ]
[ 3, false ]
[ 4, true ]
[ 5, true ]
...
*/

• switchMap

const a = interval(1000, true);
const b = a.switchMap( x => interval(300, true).mapTo(x) );
b.listen( true, console.log );

/*
0
0
0
0
1
1
1
1
2
2
*/

/*
interval   : 0 |0---------1---------2---------...

(mapped-1) : 0 |0--0--0--0--0--0--0--0--0--0--...
(mapped-2) : 0           |1--1--1--1--1--1--1-...
(mapped-3) : 0                     |2--2--2--2...
...
    --- switchMap & mapTo ---
         [0,0] |0--0--0--01--1--1--12--2--2--2...
*/

• flatMap

const a = interval(1000, true);
const b = a.flatMap( x => interval(300, true).mapTo(x) );
b.listen( true, console.log );

/*
0
0
0
0
1
0
1
0
1
0
1
2
0
1
2
0
1
2
0
1
*/

/*
interval   : 0 |0---------1---------2---------...

(mapped-1) : 0 |0--0--0--0--0--0--0--0--0--0--...
(mapped-2) : 0           |1--1--1--1--1--1--1-...
(mapped-3) : 0                     |2--2--2--2...
...
    --- flatMap & mapTo ---
         [0,0] |0--0--0--01-01-01-012012012012012012012012012
*/

• every, some

const counter = interval( 500, true );
const a = counter.map( x => x % 2 === 0 );
const b = counter.map( x => x % 3 === 0 );
counter.listen( true, console.log );
every(a, b).listen( true, console.log );

/*
0
true
1
false
2
false
3
false
4
false
5
false
6
true
7
false

counter : 0   |0---1---2---3---4---5---6---7---...
a       : T   |T---F---T---F---T---F---T---F---...
b       : T   |T---F---F---T---F---F---T---F---...
every   : T   |T---F---F---F---F---F---T---F---...

const counter = interval( 500, true );
const a = counter.map( x => x % 2 === 0 );
const b = counter.map( x => x % 3 === 0 );
counter.listen( true, console.log );
some(a, b).listen( true, console.log );

/*
0
true
1
false
2
true
3
true
4
true
5
false
6
true
7
false
...


counter : 0   |0---1---2---3---4---5---6---7---...
a       : T   |T---F---T---F---T---F---T---F---...
b       : T   |T---F---F---T---F---F---T---F---...
some    : T   |T---F---T---T---T---F---T---F---...

• toPromise

const a = interval( 500, true ).take( 5 );
const pr = a.toPromise();
a.listen( true, console.log );
pr.then( v => console.log('resolve', v ) );

/*
0
1
2
3
4
resolve 4
*/

• toObservable

const a = interval( 500, true ).take( 5 );
const ob = a.toObservable();
a.listen( true, v => console.log('listen', v) );
ob.subscribe( v => console.log('subscribe', v ) );

/*
listen 0
subscribe 0
subscribe 1
listen 1
subscribe 2
listen 2
subscribe 3
listen 3
subscribe 4
listen 4
*/

• once

const a = interval( 1000, true ).take( 5 );
a.listen( true, console.log );
setTimeout( () => a.once().then( v => console.log('once', v ) ), 2500 );

/*
0
1
2
3
once 3
4

interval : 0 |0-----1-----2-----3-----4-----
                             ^  ^
                             |  |
                             |  +---once resolves
                             +---once is called
*/

ToDo

• GUI application for generating RN code from data-flow graph
• add operators