merge map vs forkJoin vs CombineLatest

forkJoin:

Use Case: Parallel Requests

Use forkJoin when you need to make multiple HTTP requests or observables in parallel and wait for all of them to complete before taking action.

It is suitable for scenarios where you want to combine the results of multiple observables into a single emission.

   
  
forkJoin(observable1, observable2, ...).subscribe(([result1, result2, ...]) => {
  // Combine results and take action
});

     

mergeMap (or flatMap): Use Case: Sequential Requests

Use mergeMap when you want to map each value emitted by the source observable to an inner observable and process them concurrently.

It is useful when you are working with asynchronous tasks and want to maintain concurrency, allowing the inner observables to overlap.

   
         
sourceObservable.pipe(mergeMap(value => /* return inner observable */)).subscribe(result => {
  // Process the result of the inner observable
});     

In summary: Use forkJoin when you need to wait for multiple observables to complete and combine their results. Use mergeMap when you want to process values concurrently, especially when dealing with asynchronous tasks and maintaining concurrency is essential. Remember that the choice between these operators depends on the specific requirements of your application and the desired behavior regarding concurrency and the timing of operations. combineLatest and concatMap are different operators in RxJS, serving distinct purposes. Let's explore the key differences between them: Behavior: combineLatest:

Combines the latest values from multiple observables into an array or an object.

Emits a new value whenever any of the source observables emit a value.

All observables are considered independently, and each emission triggers a new combination.

concatMap: Maps each value emitted by the source observable to an inner observable. Waits for the inner observable to complete before moving on to the next one. Maintains the order of emission, processing values sequentially. Concurrency: combineLatest: Concurrently processes values from different observables. Emits a new combined value whenever any of the source observables emit. concatMap: Processes values sequentially, waiting for the completion of one inner observable before moving on to the next. Maintains a strict order of emission. Use Cases: combineLatest: Useful when you want to react to changes in any of the source observables and combine their latest values. Commonly used in scenarios where you need to keep track of the latest values from multiple sources. concatMap: Suitable when you want to maintain the order of emission and process values sequentially. Useful for scenarios where the order of operations is critical, such as making sequential HTTP requests. In summary, combineLatest is focused on combining the latest values from multiple observables concurrently, while concatMap is geared towards sequential processing, ensuring the order of emission. The choice between them depends on the specific requirements of your application.