Now consider we want to handle numbers in our known value set: const KNOWN_VALUES = Object.freeze(['a', 'b', 'c', 1, 2, 3]) function isKnownValue(input?: string | number) { return typeof(input) === 'string' && KNOWN_VALUES.includes(input) } Uh oh! This TypeScript compiles without errors, but it's not correct. Where as our original "naive" approach would have worked just fine. Why is that? Where is the breakdown here? It's because TypeScript's type system got in the way of the developer's initial intent. It caused us to change our code from what we intended to what it allowed. It was never the developer's intention to check that input was a string and a known value; the developer simply wanted to check whether input was a known value - but wasn't permitted to do so.

I've never felt challenged by any of my teachers. All their curriculums I've laughed at. I run circles around my teachers and most of them hated me because I'd finish my work and I'm pretty sure they hated me. I remember this lady. What was her name? I don't remember her name, but she was redheaded with glasses. She fucking hated me, man, because I'd laugh at pretty much all her work. I'd finish it in seconds and she'd get so frustrated with me because she's like, "Ugh. What am I supposed to do with you?"

Writing the uniqueness validations yourself is easy so I felt it was better to leave this up to the developer

Can we just forward/bubble all events emitted by the underlying input element?

If you want to implement a form with a superb User Experience, you have to take care of many variables:

Managing Form State (holding field information, check if a control has been touched, if the user has clicked the submit button, who owns the current focus...) can be tedious and prone to errors. We can get help from React Final Form to handle these challenges for us.

But it sounds like the library could use some way to setTouched()

Wondering how to get field state from multiple fields at once? People coming from Redux-Form might be wondering where the equivalent of Redux Form's Fields component is, as a way to get state from several fields at once. The answer is that it's not included in the library because it's so easy to write one recursively composing Field components together.

Furthermore, JSX encourages bad non-dry code. Having seen a lot of JSX over the past few months, its encourages copypasta coding.

there’s 3 steps to building software: Make it work Make it right Make it fast