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thelearner
thelearner

Reputation: 1130

When and why should I combine Reduces in Redux?

I have watched a few videos about reducers, and they all claimed that I should use only one reducer and state for my whole project and I should combine every reducer into one big reducer.

Now my question is, why would I do this? Imagine I have a big application and I combine all reducers. My combined reducer would be huge and a single state change would take quite long since we need to check every single reducer slice.

Should I really just use one reducer for a bigger project? Why should we combine them, instead of creating multiple stores, and what about the performance?

As your app grows more complex, you'll want to split your reducing function into separate functions, each managing independent parts of the state.

.combineReducers(...)

Thanks a lot.

Upvotes: 1

Views: 993

Answers (1)

markerikson
markerikson

Reputation: 67627

Per the Redux FAQ entry on the performance of "calling all reducers":

It's important to note that a Redux store really only has a single reducer function. The store passes the current state and dispatched action to that one reducer function, and lets the reducer handle things appropriately.

Trying to handle every possible action in a single function does not scale well, simply in terms of function size and readability, so it makes sense to split the actual work into separate functions that can be called by the top-level reducer.

However, even if you happen to have many different reducer functions composed together, and even with deeply nested state, reducer speed is unlikely to be a problem. JavaScript engines are capable of running a very large number of function calls per second, and most of your reducers are probably just using a switch statement and returning the existing state by default in response to most actions.

Also, from the FAQ entry on whether you should create multiple stores:

It is possible to create multiple distinct Redux stores in a page, but the intended pattern is to have only a single store. Having a single store enables using the Redux DevTools, makes persisting and rehydrating data simpler, and simplifies the subscription logic.

However, creating new stores shouldn't be your first instinct, especially if you come from a Flux background. Try reducer composition first, and only use multiple stores if it doesn't solve your problem.

Upvotes: 3

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