Evg_observable NPM

What is EVG Observable?

EVG Observable is a compact, lightweight library designed for handling asynchronous events. Despite its small size, it offers over 20 powerful techniques for event management.

Installation

Node.js

EVG Observable is available on npm. To install it, type:

$ npm install evg_observable

Browser

<script src="https://unpkg.com/evg_observable/repo/evg_observable.js"></script>

Usage

Observable simple usage

import {Observable} from "evg_observable/src/outLib/Observable";

const observable$ = new Observable('Some typed data (not only string)');

const listener1 = (value: string) => console.log('listener1:', value);
const errorHandler1 = (errorData: any, errorMessage: any) => {
    console.log(`listener1 catch ERROR: data ${errorData}`, errorMessage);
};
const subscriber1 = observable$.subscribe(listener1, errorHandler1);

const listener2 = (value: string) => console.log('listener2:', value);
const subscriber2 = observable$.subscribe(listener2);

console.log(observable$.getValue());
// Print to console - Some typed data (not only string)

observable$.next('Next typed data');
// Print to console - listener1: Next typed data
// Print to console - listener2: Next typed data

// if subscribers are not needed
subscriber1.unsubscribe();
subscriber2.unsubscribe();

// if a observable$ is not needed
observable$.destroy(); // all subscribers have automatically unsubscribed

// also if observable$ needs to be used further, but subscribers are not needed, you can use the observable$.unsubscribeAll() method

Browser simple usage

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="https://unpkg.com/evg_observable/repo/evg_observable.js"></script>
</head>
<body>
<script>
    const observable$ = new Observable('Some typed data (not only string)');

    const listener1 = (value) => console.log('listener1:', value);
    const subscriber1 = observable$.subscribe(listener1);

    const listener2 = (value) => console.log('listener2:', value);
    const subscriber2 = observable$.subscribe(listener2);

    console.log(observable$.getValue());
    // Print to console - Some typed data (not only string)

    observable$.next('Next typed data');
    // Print to console - listener1: Next typed data
    // Print to console - listener2: Next typed data

    // if subscribers are not needed
    subscriber1.unsubscribe();
    subscriber2.unsubscribe();

    // if a observable$ is not needed
    observable$.destroy(); // all subscribers have automatically unsubscribed

    // also if observable$ needs to be used further, but subscribers are not needed, you can use the observable$.unsubscribeAll() method
</script>
</body>
</html>

Observable pipe usage

pipe().setOnce()

Observable will send a value to the subscriber only once, and the subscriber will unsubscribe.

import {Observable} from "evg_observable/src/outLib/Observable";

const observable$ = new Observable('Some typed data (not only string)');
const listener1 = (value: string) => console.log('listener1:', value);
const listener2 = (value: string) => console.log('listener2:', value);

const subscriber1 = observable$
    .pipe()
    .setOnce()
    .subscribe(listener1);
const subscriber2 = observable$.subscribe(listener2);

console.log(observable$.getValue());
// Print to console - Some typed data (not only string)

observable$.next('Next1 typed data');
// Print to console - listener1: Next1 typed data
// Print to console - listener2: Next1 typed data

observable$.next('Next2 typed data');
// Print to console - listener2: Next2 typed data

// subscriber1 is automatically unsubscribed after first usage

pipe().unsubscribeByNegative(condition)

Observable will send a value to the subscriber as long as the condition is positive, on the first negative result, the subscriber will unsubscribe.

import {Observable} from "evg_observable/src/outLib/Observable";

const observable$ = new Observable('Some typed data (not only string)');
const listener1 = (value: string) => console.log('listener1:', value);
const listener2 = (value: string) => console.log('listener2:', value);
let isPositive = true;

const subscriber1 = observable$
    .pipe()
    .unsubscribeByNegative(() => isPositive)
    .subscribe(listener1);
const subscriber2 = observable$.subscribe(listener2);

console.log(observable$.getValue());
// Print to console - Some typed data (not only string)

observable$.next('Next1 typed data');
// Print to console - listener1: Next1 typed data
// Print to console - listener2: Next1 typed data

observable$.next('Next2 typed data');
// Print to console - listener1: Next2 typed data
// Print to console - listener2: Next2 typed data

isPositive = false;
observable$.next('Next3 typed data');
// Print to console - listener2: Next3 typed data

// subscriber1 is automatically unsubscribed when negative condition

pipe().unsubscribeByPositive(condition)

Observable will send a value to the subscriber as long as the condition is negative, on the first positive result, the subscriber will unsubscribe.

import {Observable} from "evg_observable/src/outLib/Observable";

const observable$ = new Observable('Some typed data (not only string)');
const listener1 = (value: string) => console.log('listener1:', value);
const listener2 = (value: string) => console.log('listener2:', value);
let isPositive = false;

const subscriber1 = observable$
    .pipe()
    .unsubscribeByPositive(() => isPositive)
    .subscribe(listener1);
const subscriber2 = observable$.subscribe(listener2);

console.log(observable$.getValue());
// Print to console - Some typed data (not only string)

observable$.next('Next1 typed data');
// Print to console - listener1: Next1 typed data
// Print to console - listener2: Next1 typed data

observable$.next('Next2 typed data');
// Print to console - listener1: Next2 typed data
// Print to console - listener2: Next2 typed data

isPositive = true;
observable$.next('Next3 typed data');
// Print to console - listener2: Next3 typed data

// subscriber1 is automatically unsubscribed when positive condition

pipe().emitByNegative(condition)

Observable will send a value to the listener only if condition returns "false". There is no automatic unsubscription.

pipe().emitByPositive(condition)

Observable will send a value to the listener only if condition returns "true". There is no automatic unsubscription.

pipe().emitMatch(condition)

Observable will send a value to the subscriber only if the return value of the condition matches the data being sent. In this case, there is no automatic unsubscription.

import {Observable} from "evg_observable/src/outLib/Observable";

const observable$ = new Observable('Some typed data (not only string)');
const listener1 = (value: string) => console.log('listener1:', value);
const listener2 = (value: string) => console.log('listener2:', value);
const TARGET_DATA = 'TARGET_DATA';

const subscriber1 = observable$
    .pipe()
    .emitMatch(() => TARGET_DATA)
    .subscribe(listener1);
const subscriber2 = observable$.subscribe(listener2);

console.log(observable$.getValue());
// Print to console - Some typed data (not only string)

observable$.next('Next1 typed data');
// Print to console - listener2: Next1 typed data

observable$.next('Next2 typed data');
// Print to console - listener2: Next2 typed data

observable$.next(TARGET_DATA);
// Print to console - listener1: TARGET_DATA
// Print to console - listener2: TARGET_DATA

observable$.next('Next4 typed data');
// Print to console - listener2: Next4 typed data

observable$.next(TARGET_DATA);
// Print to console - listener1: TARGET_DATA
// Print to console - listener2: TARGET_DATA

Ordered observable

Ordered observable - differs from Observable in that it allows you to emit messages in a given order. In general, they are the same.

import {OrderedObservable} from "evg_observable/src/outLib/OrderedObservable";

const observable$ = new OrderedObservable('Some typed data (not only string)');
const listener1 = (value: string) => console.log('listener1:', value);
const listener2 = (value: string) => console.log('listener2:', value);
const listener3 = (value: string) => console.log('listener3:', value);
const listener4 = (value: string) => console.log('listener4:', value);
const listener5 = (value: string) => console.log('listener5:', value);

const subscriber1 = observable$.subscribe(listener1);
const subscriber2 = observable$.subscribe(listener2);
const subscriber3 = observable$.subscribe(listener3);
const subscriber4 = observable$.subscribe(listener4);
const subscriber5 = observable$.subscribe(listener5);

observable$.next('SOME DATA');
// Default emission behavior with default order = 0 for all subscribers
// Print to console - listener1: SOME DATA
// Print to console - listener2: SOME DATA
// Print to console - listener3: SOME DATA
// Print to console - listener4: SOME DATA
// Print to console - listener5: SOME DATA

// We can change the default order of emission
subscriber1.order = 50;
subscriber2.order = 40;
subscriber3.order = 30;
subscriber4.order = 20;
subscriber5.order = 10;
observable$.next('SOME DATA');
// Print to console - listener5: SOME DATA
// Print to console - listener4: SOME DATA
// Print to console - listener3: SOME DATA
// Print to console - listener2: SOME DATA
// Print to console - listener1: SOME DATA

// Also we can use observable$.setDescendingSort() or observable$.setAscendingSort()

//Thus, we can control the order in which the data is received by the listeners.

Collector

You can also use the subscriber collector for convenience.

import {Observable} from "evg_observable/src/outLib/Observable";
import {Collector} from "evg_observable/src/outLib/Collector";

const collector = new Collector();
const observable$ = new Observable('Some typed data (not only string)');
const listener1 = (value: string) => console.log('listener1:', value);
const listener2 = (value: string) => console.log('listener2:', value);
const listener3 = (value: string) => console.log('listener3:', value);
const listener4 = (value: string) => console.log('listener4:', value);
const listener5 = (value: string) => console.log('listener5:', value);

collector.collect(
    observable$.subscribe(listener1),
    observable$.subscribe(listener2),
    observable$.subscribe(listener3),
    observable$.subscribe(listener4),
    observable$.subscribe(listener5)
);

observable$.next('SOME DATA');
// Default emission behavior with default order = 0 for all subscribers
// Print to console - listener1: SOME DATA
// Print to console - listener2: SOME DATA
// Print to console - listener3: SOME DATA
// Print to console - listener4: SOME DATA
// Print to console - listener5: SOME DATA

// ... some code ...
// ... some code ...
// ... some code ...

collector.destroy();
observable$.next('SOME DATA');
// NOTHING Print to console 

// All subscribers automatically unsubscribes
// Also, if there is a need to use the collector further, instead of destroying it, you can use collector.unsubscribeAll().
// To unsubscribe one subscriber, you can use: collector.unsubscribe(subscriber).

Methods

Observable

method	will return	description
`.subscribe(listener)`	subscriber	subscribe listener to observable
`.unSubscribe(subscriber)`	void	unsubscribe listener from observable
`.unsubscribeAll()`	void	unsubscribe all listeners from the current observable
`.next(value)`	void	emit data to listeners
`.stream(value[])`	void	pass data to listeners in parts of the array
`.getValue()`	value	will return the last value sent, or the value that was set during initialization
`.size()`	number	will return the current number of subscribers
`.disable()`	void	disable emission
`.enable()`	void	enable emission
`.isEnable`	boolean	read-only field that shows the state of the observer
`.destroy()`	void	unsubscribe all listeners from the current observable and destroy it
`.isDestroyed`	boolean	read-only field that shows the kill state of the observer
`.pipe()`	pipe condition object	returns an object with which you can customize the subscriber's behavior

Observable`.pipe()`

method	will return	description
`.setOnce()`	pipe subscribe object	observable will send a value to the subscriber only once, and the subscriber will unsubscribe.
`.unsubscribeByNegative(*condition)`	pipe subscribe object	observable will send a value to the subscriber as long as the condition is positive, on the first negative result, the subscriber will unsubscribe
`.unsubscribeByPositive(*condition)`	pipe subscribe object	observable will send a value to the subscriber as long as the condition is negative, on the first positive result, the subscriber will unsubscribe
`.emitByNegative(*condition)`	pipe subscribe object	observable will send a value to the listener only if condition returns "false", there is no automatic unsubscription
`.emitByPositive(*condition)`	pipe subscribe object	observable will send a value to the listener only if condition returns "true", there is no automatic unsubscription
`.emitMatch(*condition)`	pipe subscribe object	observable will send a value to the subscriber only if the return value of the condition matches the data being sent, in this case, there is no automatic unsubscription
`.subscribe(listener)`	subscriber	subscribe listener to observable

*condition - this is a function that should return a value that will affect the behavior of the subscriber

Observable subscriber

method	will return	description
`.unsubscribe()`	void	unsubscribe listener from observable

Ordered observable

Has the same methods as Observable.

Ordered observable subscriber

Has the same methods as subscriber. But there is an "order" field and two new methods.

field	type	description
`.order`	number	Determines the order in which the subscriber is called, the subscriber with the lowest ordinal number is called first, the subscriber with the highest ordinal number is called last.

method	will return	description
`.setAscendingSort()`	boolean	set order by ascending sort
`.setDescendingSort()`	boolean	set order by descending sort

Collector

method	will return	description
`.collect( ...subscribers)`	void	collects subscribers
`.unsubscribe(subscriber)`	void	unsubscribe a subscriber from it's observable
`.unsubscribeAll()`	void	unsubscribe all subscribers from their observables
`.destroy()`	void	unsubscribe all subscribers and destroy collector