Custom Middleware

Redux Middlware

If you want to write middleware that is compatible with Redux in general, you can just follow the Redux documentation.

You may want to consider exporting your middleware with one of the utilites for applying the middleware to a specific layer if you are aware of a specific requirement your middleware has.

Redux Subspace Middleware

Although Redux Subspace works with standard Redux middleware, you can also write Redux Subspace specific middleware. The main difference between Redux middleware and Redux Subspace middleware, is Redux middleware only allows you to modify the dispatch pipeline, whereas Redux Subspace middleware can modify both the dispatch and the getState pipelines.

dispatch Middleware

dispatch middleware can be written the same as standard Redux middleware:

const middleware = (subspace) => (next) => (action) => next(action)

We can also write it more explicilty as:

const middleware = (subspace) => ({
    dispatch: (next) => (action) => next(action)
})

getState Middleware

getState middleware is similar to the more explicit dispatch middleware:

const middleware = (subspace) => ({
    getState: (next) => () => next()
})

Combining dispatch and getState Middleware

It is possible to write a single middleware that extends both pipelines:

const middleware = (subspace) => ({
    dispatch: (next) => (action) => next(action),
    getState: (next) => () => next()
})