This is coding 101: Write/include only the code you need. No more, no less. To quote ESR (as much as I hate doing so), "Don't just do something, stand there!"

And yes, security and error checking are necessary. Anybody who says otherwise should be drawn, quartered, shot, and fired.

As much as I like this post, a framework sometimes has some value. If you're writing a true SPA, it'll only be loaded once, and something like React or Mithril is nice for a bit of structure. Mithril in particular, due to its small size, is handy.