They essentially created a unique type for every. single. variable. I'm talking like, if you needed string constant for an error message on Input 1 on Form 3, there was an ErrorLoadingMessageForInput1OnForm3 type declared for that instead of defining it as a string. The types were never reused - like if you had the same error message on Form 2, there'd be a separate ErrorLoadingMessageForInput1OnForm2 type for the same string. And then every interaction between any 2 variables had its own type of types. Like if Form 3 was displaying the error message, there'd be a type for Form3DisplayingErrorLoadingMessageForInput1OnForm3. Which of course, is distinct from Form3DisplayingErrorLoadingMessageForInput1OnForm3AndErrorLoadingMessageForInput2OnForm3. And then those types were combined to create even more types, and so on until you had literally tens of thousands of lines of _just_ type declarations for variables and every possible permutation of UI state sitting atop a recursive pyramid of smaller subsets of the permutations (and so on until it eventually got to actual variable declarations). An then all that was piped through the craziest clusterfuck of redux butchery imaginable with a similar dynamic of explosively exponential growth of references and types and states and properties and so on. Like I said, it still hurts my brain thinking about it.
That's not code written by an experienced dev like you said.
They might have worked long enough to think they're experienced, but this is proof they're just terrible if not a complete hack that's in the wrong line of business.
Yeah...unfortunately they managed to fool me (and the rest of the team) in the hiring process. It was a nice day when they were finally forced off but also unfortunately it's been an ongoing, multi-year scourge dealing with the codebase they left behind. It works just well enough that it's not worth scrapping and totally replacing yet (at least as far as management is concerned) but it's virtually impossible to make changes/updates to it and maintain your sanity.
Holy moly. I've seen some bloat but that takes the cake.