Operators

Below is the list of operators that this library has to offer:

• batchForkJoin
• sequential

1. batchForkJoin

This operator is used to process a forkJoin in batches. The regular rxjs operator 'forkJoin' has a major drawback i.e. it executes all observables at once and there is no way to make them execute in batches. This custom operator 'batchForkJoin' overcomes this drawback.

Parameters

| Parameter | Type | Description | | :-------- | :------- | :------------------------- | | observables | Observable<T> | Required. Array of observables that need to be processed in batches | | batchCount | Number | Optional. This number tells the operator to split input observables into how many batches. If this parameter is empty, batchForkJoin will operate like a regular forkJoin |

batchForkJoin(observables, batchCount)

Takes an array of observables, execute them into a user-defined number of batches, executes them and returns the responses in the same way i.e. in batches

Example

Let us consider a scenario where a developer wants to process 20 requests in batches where each batch contains 5 requests.

To achieve this, we will use batchForkJoin operator with two parameters where first parameter observables is a single array of 20 observables and second parameter batchCount is 5. With this info, batchForkJoin will split the input array into a 4 batches with 5 observables in each batch and will sequentially execute all batches. This is demonstrated in the code below:

Example below explains how to use the operator:

 /**
  * Function to execute requests in batches of 5.
  *
  * Note: `InputType` is the type of request in each observable and
  * and `OutputType` is the type of response resulting from execution of each input observable
  */
  function processRequests(requests: Array<Observable<InputType>>): void {
    const subscription = batchForkJoin(requests, 5).subscribe({
        next: (resultInBatches: Array<OutputType>) => {
            // As we have x number  of batches, next callback is execute x times.
            // Now handle the response same way as you would in a regular forkJoin
        },
        complete: () => {
            // This will indicate completion of batchForkJoin.
            // If `sequential` operator is piped then there are other ways to wait for its completion.
        }
    })
  }

2. sequential

This operator is used to process an array of observables sequentially one-by-one. Normally you would use rxjs's from and concatMap opertors in a combination to achieve this but to get rid of that mess and have a clean code, you can use this custom operator.

Parameters

| Parameter | Type | Description | | :-------- | :------- | :------------------------- | | observables | Observable<T> | Required. Array of observables that need to be processed sequentially one-by-one |

sequential(observables)

Takes an array of observables, and executes them one-by-one sequentially

Example

Let us consider a scenario where a developer wants to process 20 requests one by one sequentially where second request is triggered only when response of first request is achieved.

To achieve this, we will use sequential operator with only one parameter observables which is an array of 20 observables. With this info, sequential will execute each observable one-by-one and return response in the same way i.e. one-by-one. This is demonstrated in the code below:

Example below explains how to use the operator:

 /**
  * Function to execute requests one-by-one.
  *
  * Note: `InputType` is the type of request in each observable and
  * and `OutputType` is the type of response resulting from execution of each input observable
  */
  function processRequests(requests: Array<Observable<InputType>>): void {
    const subscription = sequential(requests).subscribe({
        next: (resultOfEachRequest: OutputType) => {
            // As we have x number requests, next callback is execute x times.
            // Now handle the response same way as you would in a `from` operator
        },
        complete: () => {
            // This will indicate completion of from operator.
            // If `sequential` operator is piped then there are other ways to wait for its completion.
        }
    })
  }