Req Params

This property is an object containing properties mapped to the [named route "parameters"](/{{ page.lang }}/guide/routing.html#route-parameters). For example, if you have the route /user/:name, then the "name" property is available as req.params.name. This object defaults to {}.

// GET /user/tj
console.dir(req.params.name)
// => 'tj'

When you use a regular expression for the route definition, capture groups are provided as integer keys using req.params[n], where n is the n^th capture group. This rule is applied to unnamed wild card matches with string routes such as /file/*:

// GET /file/javascripts/jquery.js
console.dir(req.params[0])
// => 'javascripts/jquery.js'

Named capturing groups in regular expressions behave like named route parameters. For example the group from /^\/file\/(?<path>.*)$/ expression is available as req.params.path.

If you need to make changes to a key in req.params, use the [app.param](/{{ page.lang }}/4x/api.html#app.param) handler. Changes are applicable only to [parameters](/{{ page.lang }}/guide/routing.html#route-parameters) already defined in the route path.

Any changes made to the req.params object in a middleware or route handler will be reset.

{% include admonitions/note.html content="Express automatically decodes the values in req.params (using decodeURIComponent)." %}