Which RxJS Operators to use in your NgRx Effects

When creating NgRx effects you need to decide which RxJS operators to use. There are a lot of RxJS operators but the ones that we are going to use are: mergeMap, concatMap, exhaustMap, and switchMap. Each of these have recommended use cases in order to avoid race conditions.

Operator Explanation

Before we look at when to use each of the operators, lets look at what each of the operators does.

• mergeMap: subscribe immediately, never cancel or discard
• concatMap: subscribe after the last one finishes
• exhaustMap: discard until the last one finishes
• switchMap: cancel the last one if it has not completed

Operator Usage

Now lets look at when to use each of the operators

• mergeMap: deleting items
• concatMap: updating or creating items
• exhaustMap: non-parameterized queries
• switchMap: parameterized queries

By following these recommendations on usage, you will avoid race conditions within your effects.