We've been doing the O(n) thing forever with PHP and CGI since 1995, the issue is that it required constant whole-page reloads and was a poor experience that got worse the more interactive your webapps got. React let you do the same thing but made it fast(ish) with local updates
We actually see similar innovations on the FP side as well, with persistent data structures that allow structural sharing so your "copy and update" operations can be fast enough to be usable (even if still not nearly as fast as in-place mutation)
We actually see similar innovations on the FP side as well, with persistent data structures that allow structural sharing so your "copy and update" operations can be fast enough to be usable (even if still not nearly as fast as in-place mutation)