The core concept of Marble.js assumes that almost everything is a stream. The main building block of the whole framework is an Effect, which is just a function that returns a stream of events.
The purely functional languages like Haskell expresses side effects such as IO and other stateful computations using monadic actions. With the big popularity of RxJS Observable monad, you can create a referential transparent program specification made up of functions that may produce side effects like network, logging, database access, etc. Using its monadic nature we can map I/O operations over effects and flat them to bring in other sequences of operations. Marble.js is a functional reactive framework, that's why RxJS is a first class citizen here. It’s a much more powerful and feature-rich monad than IO that implements the basic abstract interface as well as a ton of additional functionalities for manipulating sequences of events over time.
When looking at Marble.js you can ask: "Why do we need RxJS for HTTP?". Despite the single event nature of basic HTTP, there are are no contraindications against using it for single events. In Marble, RxJS is used as a hammer for expressing asynchronous flow with monadic manner, even if you have to deal with only one event passing over time. Marble.js doesn't operate only over basic HTTP protocol but can be used also for both WebSocket and event sourcing purposes, where the multi-event nature fits best. Don't be scared of the complexity and abstractions presented in RxJS API — the Marble.js framework, in general, is incredibly simple. For more details about its specifics, please visit the next chapters that will guide you through the framework environment and implementation details.
For those who are curious about the framework name - it comes from a popular way of visually expressing the time-based behavior of event streams, aka marble diagrams. This kind of domain-specific language is a popular way of testing asynchronous streams, especially in RxJS environments.
Marble.js requires node v8.0 or higher:
$ npm i @marblejs/core rxjs
or if you are a hipster:
$ yarn add @marblejs/core rxjs
To view the example project, visit the example repository.