Reading 10 - AvreyBrown-401-advanced-javascript/seattle-javascript-401d32 GitHub Wiki

router.param(name, callback) Adds callback triggers to route parameters, where name is the name of the parameter and callback is the callback function. Although name is technically optional, using this method without it is deprecated starting with Express v4.11.0 (see below).

The parameters of the callback function are:

req, the request object. res, the response object. next, indicating the next middleware function. The value of the name parameter. The name of the parameter.

Param callback functions are local to the router on which they are defined. They are not inherited by mounted apps or routers. Hence, param callbacks defined on router will be triggered only by route parameters defined on router routes.

A param callback will be called only once in a request-response cycle, even if the parameter is matched in multiple routes, as shown in the following examples.

router.route(path) Returns an instance of a single route which you can then use to handle HTTP verbs with optional middleware. Use router.route() to avoid duplicate route naming and thus typing errors.