Can the operator pipeline generate interim observables in a manner akin to how filter, map, and reduce generate interim arrays?

Question

Can the operator pipeline generate interim observables in a manner akin to how filter, map, and reduce generate interim arrays?

I need some clarification regarding the efficiency of operator pipelines in RxJS.

Based on my current understanding, each operator within the pipeline receives an observable and generates a new (potentially modified) observable to pass on to the next operator. This process is similar to how JavaScript's filter, map, and reduce functions work, ensuring the original observable or array remains pure and untouched.

The RxJS Documentation supports this notion at: https://rxjs-dev.firebaseapp.com/guide/operators

A Pipeable Operator is a function that takes an Observable as its input and returns another Observable. It is a pure operation: the previous Observable stays unmodified.

When dealing with lengthy operator pipelines, the creation of intermediate observables may seem resource-intensive.

Furthermore, I am currently studying the book 'Reactive Programming with RxJS 5' by Sergi Mansilla. Although RxJS has advanced to version 6.5.3, the fundamental mechanisms are likely unchanged.

The book discusses the efficiency of pipelines, stating that they do not produce intermediate Observables. Instead, all operations are applied to each element simultaneously. For instance, the operator take(amount) completes the stream after extracting the initial amount of elements. Moreover, it mentions the concept of lazy evaluation, which involves traversing the source observable stream just once or until the take condition is met.

import * as rxCore from 'https://dev.jspm.io/rxjs@6/_esm2015/index';
import * as rxOps from 'https://dev.jspm.io/rxjs@6/_esm2015/operators';

const numberStream = rxCore.range(0, 10);
numberStream.pipe(
    rxOps.map(number => number * number),     //creates Observable with [0,1,4,9,16,25,36,49,64,81]
    rxOps.filter(number => number % 2 === 0), //creates Observable with [0,4,16,36,64]
    rxOps.take(3)         //completes after [0,4,16]
).subscribe(console.log); //logs 0, 4, 16

Is there any generation of intermediate observables within this operator pipeline? Or does only the final pipeline create a new observable while leaving the numberStream unaffected? What exactly is happening in this scenario?

javascript rxjs observable pipeline

Answer 1

Answer №1

When creating a custom operator to use in the pipe() method, it is important to consider how the function will modify or append operations to the source observable.

source=>source.pipe(...)

The custom operator should return an observable that has been modified by the additional operations applied within the function. It is worth noting that the end result of the pipe will still only have one source observable passed through.

Answer 2

When creating a custom operator to use in the pipe() method, it is important to consider how the function will modify or append operations to the source observable.

source=>source.pipe(...)

The custom operator should return an observable that has been modified by the additional operations applied within the function. It is worth noting that the end result of the pipe will still only have one source observable passed through.

Answer 3

Answer №2

It seems that nearly every RxJS operator generates a new intermediate Observable. To date, I have yet to come across an operator that does not follow this pattern, leading me to believe that it is a standard behavior for all of them.

For instance, the map() operator internally triggers the execution of the lift method. The purpose of the lift method is to create a fresh Observable and return it, designating the current Observable as the "source" Observable.

In practical terms, when you use operators like range, it initiates one Observable; meanwhile, map, filter, and take introduce three distinct Observables, each tied back to the previous one through the "source" connection. Therefore, the "source" Observable for map originates from the Observable created by range, forming a chain reaction.

Hence, upon subscribing to any given Observable, the system attempts to engage with the operator linked to the "source" Observable. For operations like map, the process unfolds by triggering its call method, which in turn subscribes to the corresponding source Observable. In practice, this subscription trickles down to the initial Observable (lacking a direct "source"), thus eluding any operator application.

Given extensive operator pipelines, creating intermediary observables might appear resource-intensive.

The good news is that Intermediate Observables consist of plain JavaScript objects, offering a lightweight structure that poses minimal performance concerns even when stacking numerous objects together. Moreover, Observables remain inert until an event prompts action, ensuring efficiency.

A section in a literature discusses pipeline efficiency, claiming that observable pipelines bypass intermediate Observable creation and instead execute operations on each element continuously.

In my view, while some validity exists in this claim, the reality is more nuanced. Operators do apply functions to individual elements, but rather than operating via a singular Observable entity, they establish multiple ones for enhanced processing. This paradigm shift appears prevalent in modern iterations of RxJS beyond version 5.

Answer 4

It seems that nearly every RxJS operator generates a new intermediate Observable. To date, I have yet to come across an operator that does not follow this pattern, leading me to believe that it is a standard behavior for all of them.

For instance, the map() operator internally triggers the execution of the lift method. The purpose of the lift method is to create a fresh Observable and return it, designating the current Observable as the "source" Observable.

In practical terms, when you use operators like range, it initiates one Observable; meanwhile, map, filter, and take introduce three distinct Observables, each tied back to the previous one through the "source" connection. Therefore, the "source" Observable for map originates from the Observable created by range, forming a chain reaction.

Hence, upon subscribing to any given Observable, the system attempts to engage with the operator linked to the "source" Observable. For operations like map, the process unfolds by triggering its call method, which in turn subscribes to the corresponding source Observable. In practice, this subscription trickles down to the initial Observable (lacking a direct "source"), thus eluding any operator application.

Given extensive operator pipelines, creating intermediary observables might appear resource-intensive.

The good news is that Intermediate Observables consist of plain JavaScript objects, offering a lightweight structure that poses minimal performance concerns even when stacking numerous objects together. Moreover, Observables remain inert until an event prompts action, ensuring efficiency.

A section in a literature discusses pipeline efficiency, claiming that observable pipelines bypass intermediate Observable creation and instead execute operations on each element continuously.

In my view, while some validity exists in this claim, the reality is more nuanced. Operators do apply functions to individual elements, but rather than operating via a singular Observable entity, they establish multiple ones for enhanced processing. This paradigm shift appears prevalent in modern iterations of RxJS beyond version 5.

Can the operator pipeline generate interim observables in a manner akin to how filter, map, and reduce generate interim arrays?

Answer №1

Answer №2

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