@ngspot/rxjs

A library providing a few useful RxJS operators.

Installation

NPM

npm install @ngspot/rxjs

Yarn

yarn add @ngspot/rxjs

Operators:

• filterOutNullish - type safe operator for filtering out nullish values
• deferredStartWith - the same as startWith, but takes the first value in a callback, which allows to evaluate it lazily
• conditionalStartWith - the same as deferredStartWith, but the first argument is a callback returning a boolean. If boolean is evaluated to true, startWith is applied with a result of a callback of the second argument
• log$ - logs values passing through this operator
• mutationObserver - observable creator. Wraps native MutationObserver
• resizeObserver - observable creator. Wraps native ResizeObserver
• zoneFull - enters the stream into Angular Zone
• zoneFree - exits the stream from Angular Zone

Usage

import { filterOutNullish } from '@ngspot/rxjs/operators';

myObservable$.pipe(filterOutNullish());

Decorators

@Share()

This decorator comes handy when you expect a function that returns a completable observable to share that observable for a unique set of parameters of the function.

In the example below only 2 http network requests will be made.

import { Share } from '@ngspot/rxjs/decorators';

class MyApi {
  constructor(private http: HttpClient) {}

  @Share()
  makeCall(param1: number, param2: number) {
    return this.http.get(`/api/${param1}/${param2}`);
  }
}

class BusinessLogic {
  constructor(private api: MyApi) {
    api.makeCall(1, 2).subscribe();
    api.makeCall(1, 2).subscribe();
    api.makeCall(1, 3).subscribe();
  }
}

There might be a use-case when you'd want to disable the functionality of @Share decorator based on the function arguments. To achieve this you can provide the when option to specify the condition when the observable should be shared:

In the example below the observable will only be shared when the param1 is not equal to param2.

@Share({ when: (param1, param2) => param1 !== param2 })
makeCall(param1: number, param2: number) {
  return this.http.get(`/api/${param1}/${param2}`);
}

The context of the when callback function is the context of the class instance. The signature of the of when callback has the same signature as the method that the decorator is applied to.

With the implementation above, two HTTP requests will be made in the example below:

class BusinessLogic {
  constructor(private api: MyApi) {
    api.makeCall(1, 1).subscribe();
    api.makeCall(1, 1).subscribe();
  }
}

License

MIT © Dmitry Efimenko