What Is a flatMap

flatMap , as it can be guessed by its name, is the combination of a map and a flat operation. That means that you first apply a function to your elements, and then flatten it. Stream. map only applies a function to the stream without flattening the stream.

Why do we need flatMap?

Using flatMap lets you chain functions of the shape A => M[B] to oblivion (in the previous example A and B are Int , and M is Option ).

What is the difference between map and flatMap in angular?

So what’s the exact difference between map and flatMap: map transforms items emitted by an Observable by applying a function to each item whereas flatmap: Applies a specified function to each emitted item and this function in turn returns an Observable for each item.