From 7af31c26045e605a5013fe96fe8478cdc130eeb9 Mon Sep 17 00:00:00 2001
From: Hage Yaapa <captain@hacksparrow.com>
Date: Mon, 19 Jun 2017 12:54:06 +0530
Subject: [PATCH] Guidelines for setting state in req.params

---
 _includes/api/en/4x/req-params.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/_includes/api/en/4x/req-params.md b/_includes/api/en/4x/req-params.md
index bfc27236..aed482f3 100644
--- a/_includes/api/en/4x/req-params.md
+++ b/_includes/api/en/4x/req-params.md
@@ -15,3 +15,7 @@ When you use a regular expression for the route definition, capture groups are p
 req.params[0]
 // => "javascripts/jquery.js"
 ```
+
+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.