title: Default error handler for node express
body: <p>I've read the <a href="https://expressjs.com/en/guide/error-handling.html" rel="nofollow noreferrer">error handling guidance</a> given for the <a href="https://expressjs.com/" rel="nofollow noreferrer"><code>express</code></a> module, but would like to dig a little deeper and see exactly what the default error handler in <code>express</code> actually does (and hence what my custom error handler should and shouldn't do, if it can pass on some of the basic error handling procedure on to the default handler).  It may just be showing my ignorance, but I can't for the life of me find where the default error handler is actually defined in the <a href="https://github.com/expressjs/express" rel="nofollow noreferrer"><code>express</code> source code</a>.  Please can someone help me out here.</p>