If you use React, understand custom hooks. They make error handling, auth, a lot cleaner, and you can easily switch from ContextProviders to reducers if need be.

Another thing, read about Promise.all() for real concurrency, just chaining async calls is a bottleneck, if the calls are independent.

Build stuff. Skill honing comes from doing. Expertise does not come from reading books.

Make stuff. Figure out where your ideas break down and how to work around that.

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