Javascript – Accessing req parameters for` Node.js` route before request is sent

In a Node.js server routes get request data as follows:

router.get(
'/dog',
 (req, res) => {
  req.something...
}
)

For debugging purposes, I want to inspect what gets sent as the req object for a call like the following:

fetch(/app/dog)
.then(...)

Is there a way for me to access the req parameters before the request is sent? (Presumably I could do such debugging in my route, but I’m wanting to perform this inspection before making the fetch call). Thanks!