Already mentioned, but wanted to +1 on getting rid of the any disease.

Additionally, turning on strict mode could be really interesting to better take advantage of TypeScript.

No any in the repo - neither explicit nor implicit

So I completely agree, but there are certainly some places where it is much more of a concern than others. For example, anything that the user provides (their data, their dataKey, their custom stuff) is less important to type correctly than the things we provide users (callback functions, payloads, props we actually so stuff with).

+1 for getting to a point where we can turn on strict mode.

@nikolasrieble happy to take this on if no one else has already

@csdiehl this one will be harder to tackle than it looks on the surface. The codebase is littered with bad types and if we change those bad types we'll break how consumers are currently using them. If you want to try to do this we either need to

1. Ensure non-breaking changes
   Or
2. Do this as if it would go into 3.x.

Type changes are hard to make non-breaking so 2 would be easier. 3.x will have a lot of other changes though and that will make huge merge conflicts for this. We may be better off making types better after refactoring than doing it now. Or do it in a non-breaking way

ok - @ckifer since I'm new to contributing to this project, I'll look for smaller issues to tackle first. Someone else can take this