Common Lisp is dynamically typed but it matters far less compared to a language like Javascript. Again that is because the development process is very different. You are not writing code, compiling it and hope it works. You are modifying a Lisp image as it runs, so you are working at a much finer grain where type safety is not that required. I have not faced major typing related issues and also in the rare occasions when you do face them, you can simply update the image while it is running.
Ah, that's a really interesting approach. With JavaScript and Python, you re-run the code or re-start the server or refresh the page (there's no compile step), but I've way too frequently run into type errors in project both small and large (but especially larger ones). I've also found it significantly harder to understand code written by other (i.e. to understand or know what the structure of objects being passed around is)--my solution often was to use a debugger and set a breakpoint and inspect the structure of the object (of course, this was experientially a lot more cumbersome than using a statically typed language), but is the idea with CL kind of similar, in that you sort of inspect the program while it runs, but you also have a JVM HotSwap like capability?
