Flagsmith: Fetch error: ReferenceError: XMLHttpRequest is not defined about flagsmith-js-client

[nvsd]

@dabeeeenster Sorry about that.

This issue should make quite a bit more sense here!

[kyle-ssg]

Hey @nvsd.

Thanks for submitting an issue, there were a few adjustments you needed to make in order to get this to work. I've noted them in a pull request I've made to your example.

In case this is visited by others facing this issue, the following are good resources to check when developing in Next.js:

https://docs.flagsmith.com/clients/next-ssr
https://github.com/Flagsmith/flagsmith-js-client/tree/main/examples/nextjs

The solution

https://github.com/nvsd/flagsmith-repro/pull/1

• With SSR and technologies such as next you should use flagsmith/isomorphic which deals with a mixture of node and frontend
• Since fetching flags is asynchronous you'd need to either show a loader on SSR or more ideally await fetching flags, I've added the latter in MyApp.getInitialProps
• In relation to the above, we can use the SSR data from Flagsmith to prevent fetching on the client if we want you could add in the like preventFetch: !!flagsmithState in the options object