How do you create custom asynchronous functions in node.js?

Question

I was unsure how node.js was able to realize what functions where async and which were not and how to create a custom async function.

Say I wanted to create a custom

Answer 1

Only native functions (with access to the event loop) are asynchronous. You would need to call one of them to get asynchronity for your callback. See What is a simple example of an asynchronous javascript function?.

If you aren't using any, there's hardly a reason to make your function asynchronous.