The choice between invoking a function within a route handler or employing a middleware for the task

I am currently exploring a potential difference in coding approaches. Let me illustrate this with an example excerpted from the express documentation: https://expressjs.com/en/guide/using-middleware.html

function logOriginalUrl (req, res, next) {
  console.log('Request URL:', req.originalUrl)
  next()
}

function logMethod (req, res, next) {
  console.log('Request Type:', req.method)
  next()
}

const logStuff = [logOriginalUrl, logMethod]
app.get('/user/:id', logStuff, (req, res, next) => {
  res.send('User Info')
})

In the above example, both logOriginalUrl and logMethod serve as middlewares. But what if I were to rewrite it like this:

function logOriginalUrl() {
  console.log('Request URL:', req.originalUrl);
}

function logMethod() {
  console.log('Request Type:', req.method);
}

app.get('/user/:id', (req, res, next) => {
  logOriginalUrl();
  logMethod();
  res.send('User Info')
})

Would there be any distinction between these two implementations? While this is a basic illustration, it can be extrapolated to various scenarios involving request manipulation or other functionalities.

What sets apart a middleware approach from directly invoking and awaiting a function within a route handler?

In theory, tasks achievable through middleware seem replicateable by simply invoking the same function within the route handler. So, what nuances do I overlook in this transition?

Answer №1

The issue with your second code is that it will result in an error due to the fact that req is deemed as undefined within the scope of both logOriginalUrl and logMethod.

If, however, you were to properly pass this information, there wouldn't be any noticeable distinction. Middlewares serve as a convenience.

They are specifically used to address common scenarios between routes and enhance the readability of the code.

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