Should I avoid calling require when responding to a request?

Question

Is requireing a module going to block every single request? According to the docs, the module is cached after the first require but I wanted to see if it's an anti-pattern to do a dynamic require when responding to a request.

Answer 1

Nope, it won't block on every request (as long as you're requiring the same module each time), and it's not an anti-pattern.

If you're loading the same module on each request, any call to require will return instantly (because the module will have already been loaded, compiled, and cached). If, however, many different modules may be required so that you don't get the benefit of caching, it may be better to do an asynchronous require.

But something like this?

function handler(req, res) { require('fs').readFile(…); }

No big deal. It's just a matter of style.