Understanding RxJS map, mergeMap, switchMap and concatMap
Mapping data is a common operation while writing your program. When you use RxJS in your code to produce your data streams it’s very likely you eventually need a way to map the data to whatever format you need it to be. RxJS comes with a ‘normal’ map function, but also has functions like mergeMap, switchMap and concatMap which all behave slightly different.
The map operator
The map operator is the most common of all. For each value that the Observable emits you can apply a function in which you can modify the data. The return value will, behind the scenes, be reemitted as an Observable again so you can keep using it in your stream. It works pretty much the same as how you would use it with Arrays. The difference is that Arrays will always be just Arrays and while mapping you get the value of the current index in the Array. With Observables the type of data can be of all sorts of types. This means that you might have to do some additional operations in side your Observable map function to get the desired result. Let’s look at some examples:
