This codebase is using TypeScript. Changes will not be merged without correct typing. If you are not sure about a particular use case let TypeScript break the build and it can be discussed in the pull request.
The TypeScript documentation is great. Have a look at it.
This code base employs a number of different testing strategies including unit, integration, browser and performance tests. Testing various aspects of the system helps to promote its quality and stability.
While code coverage is not a guarantee of code health, it is a good indicator. This code base currently sits at ~94% coverage.
This codebase is designed to be extremely performant - it is part of its DNA. It is designed to perform the smallest amount of updates possible. You can have a read about performance work done for @hello-pangea/dnd here:
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Great care has been taken to keep the library as light as possible. There could be a smaller net cost if you where already using one of the underlying dependencies.