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Curious layman here (no web dev experience). I thought the main selling point of reactive programming was that it abstracted away the need to manage state. What

Curious layman here (no web dev experience). I thought the main selling point of reactive programming was that it abstracted away the need to manage state. What problems, then, does a state management library solve in a reactive framework?

tadfisher 4y ago
Reactive programming provides the capability to react to changes in state. You still need to hold that state somewhere, mutate the state from your reactive code, and control the lifetime/scope of that state. Managing state becomes more of a concern with reactive programming, but it also becomes very explicit; this is something that traditional MVC approaches try to hide, to the detriment of anyone trying to understand the data path of your application.
- wruza 4y ago
  ELI5 why Excel can update all of the sheets from all the different data sources without overloading its user with “state management” thing and React can not?
  - azemetre 4y ago
    This talk from Rich Harris should answer most of your Qs: Rethinking reactivity https://www.youtube.com/watch?v=AdNJ3fydeao https://www.youtube.com/watch?v=AdNJ3fydeao He goes over the history of spreadsheets, reactive programming, and dunks on react.
    - deleted 4y ago
      [deleted]
    - wruza 4y ago
      I was negative in my deleted comment, but watched the video anyway (I remember skimming through it back in 2019). It answers my question only tangentially, because it doesn’t touch state management per se. The key point was, what’s the fuss about React SM and why it must be explicit in it. The video basically says that it is a nonsense which may and should be avoided. I agree, and so still don’t get what ggp is talking about.
ksbrooksjr 4y ago
Most state management libraries help you deal with the problem of sharing state between multiple components. In modern React, most components are just functions, so this boils down to passing state through deep call stacks. If you have a component A, which renders component B, which in turn renders component C, without a state management library you'd have to pass state from A to B to C (this is often called prop drilling). The longer the call stack, the more irritating this becomes. State management libraries allow component C and component A to modify, and subscribe to a shared state store. Redux et al. are effectively the reactive version of global variables.
- BigJono 4y ago
  React already has a mechanism for this (Context). It's not the primary reason to use a state management library. Any discussion that doesn't revolve around a difference between the two is akin to suggesting re-implementing a standard library call for literally no reason.
  - ksbrooksjr 4y ago
    The commenter I was replying to wasn't inquiring about why people choose third-party state management libraries in lieu of the standard context api. In fact, he's not even a web developer. He seemed to be wondering why you need a state management solution in the first place. If he had asked why people prefer Zustand, or Redux, or Recoil over React's built in context api then I would have replied accordingly. I was largely expounding upon the linked article's first list item under the heading "The problems global state management libraries need to solve". The first item in that list begins with: > Ability to read stored state from anywhere in the component tree. This is the most basic function of a state management library. It allows developers to persist their state in memory, and avoid the issues prop drilling has at scale. I would argue that the primary function of state management libraries is still sharing state between components. Third-party libraries might expose a more performant, simpler, or more intuitive api, but that's still their primary purpose. Analogously, if a non-compiler developer asked why programming languages need memory management, you wouldn't delve into the differences between reference counting and tracing garbage collection.
chrisco255 4y ago
As we know from computer science, there are two difficult problems: naming things and cache invalidation. State management is inherently difficult in web apps (I think it's inherently difficult for any complex application). They are effectively distributed systems with local caches and remote server data that need to be synced correctly in order to manage a user application at scale. That all has to align with how the presentation logic is built. It has to deal with the constraints of the web platform, etc.

tadfisher 4y ago

Reactive programming provides the capability to react to changes in state. You still need to hold that state somewhere, mutate the state from your reactive code, and control the lifetime/scope of that state. Managing state becomes more of a concern with reactive programming, but it also becomes very explicit; this is something that traditional MVC approaches try to hide, to the detriment of anyone trying to understand the data path of your application.

wruza 4y ago
ELI5 why Excel can update all of the sheets from all the different data sources without overloading its user with “state management” thing and React can not?
- azemetre 4y ago
  This talk from Rich Harris should answer most of your Qs: Rethinking reactivity https://www.youtube.com/watch?v=AdNJ3fydeao https://www.youtube.com/watch?v=AdNJ3fydeao He goes over the history of spreadsheets, reactive programming, and dunks on react.
  - deleted 4y ago
    [deleted]
  - wruza 4y ago
    I was negative in my deleted comment, but watched the video anyway (I remember skimming through it back in 2019). It answers my question only tangentially, because it doesn’t touch state management per se. The key point was, what’s the fuss about React SM and why it must be explicit in it. The video basically says that it is a nonsense which may and should be avoided. I agree, and so still don’t get what ggp is talking about.

ksbrooksjr 4y ago

Most state management libraries help you deal with the problem of sharing state between multiple components. In modern React, most components are just functions, so this boils down to passing state through deep call stacks. If you have a component A, which renders component B, which in turn renders component C, without a state management library you'd have to pass state from A to B to C (this is often called prop drilling). The longer the call stack, the more irritating this becomes. State management libraries allow component C and component A to modify, and subscribe to a shared state store. Redux et al. are effectively the reactive version of global variables.

BigJono 4y ago
React already has a mechanism for this (Context). It's not the primary reason to use a state management library. Any discussion that doesn't revolve around a difference between the two is akin to suggesting re-implementing a standard library call for literally no reason.
- ksbrooksjr 4y ago
  The commenter I was replying to wasn't inquiring about why people choose third-party state management libraries in lieu of the standard context api. In fact, he's not even a web developer. He seemed to be wondering why you need a state management solution in the first place. If he had asked why people prefer Zustand, or Redux, or Recoil over React's built in context api then I would have replied accordingly. I was largely expounding upon the linked article's first list item under the heading "The problems global state management libraries need to solve". The first item in that list begins with: > Ability to read stored state from anywhere in the component tree. This is the most basic function of a state management library. It allows developers to persist their state in memory, and avoid the issues prop drilling has at scale. I would argue that the primary function of state management libraries is still sharing state between components. Third-party libraries might expose a more performant, simpler, or more intuitive api, but that's still their primary purpose. Analogously, if a non-compiler developer asked why programming languages need memory management, you wouldn't delve into the differences between reference counting and tracing garbage collection.

chrisco255 4y ago

As we know from computer science, there are two difficult problems: naming things and cache invalidation. State management is inherently difficult in web apps (I think it's inherently difficult for any complex application). They are effectively distributed systems with local caches and remote server data that need to be synced correctly in order to manage a user application at scale. That all has to align with how the presentation logic is built. It has to deal with the constraints of the web platform, etc.