From 40197d6831ac2ef209f6ac3aaeca1edade060f66 Mon Sep 17 00:00:00 2001
From: krzysdz <krzysdz@users.noreply.github.com>
Date: Sat, 1 Nov 2025 01:09:59 +0100
Subject: [PATCH 1/6] docs(migrating-5): document req.params changes in 5.x

Fixes #2090
---
 en/guide/migrating-5.md | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/en/guide/migrating-5.md b/en/guide/migrating-5.md
index 99a5b8fb9f..faf0e3e1ca 100755
--- a/en/guide/migrating-5.md
+++ b/en/guide/migrating-5.md
@@ -71,6 +71,7 @@ You can find the list of available codemods [here](https://github.com/expressjs/
   <li><a href="#app.router">app.router</a></li>
   <li><a href="#req.body">req.body</a></li>
   <li><a href="#req.host">req.host</a></li>
+  <li><a href="#req.params">req.params</a></li>
   <li><a href="#req.query">req.query</a></li>
   <li><a href="#res.clearCookie">res.clearCookie</a></li>
   <li><a href="#res.status">res.status</a></li>
@@ -506,7 +507,7 @@ const server = app.listen(8080, '0.0.0.0', (error) => {
 
 The `app.router` object, which was removed in Express 4, has made a comeback in Express 5. In the new version, this object is a just a reference to the base Express router, unlike in Express 3, where an app had to explicitly load it.
 
-<h3 id="req.body">req.body</h3> 
+<h3 id="req.body">req.body</h3>
 
 The `req.body` property returns `undefined` when the body has not been parsed. In Express 4, it returns `{}` by default.
 
@@ -514,6 +515,22 @@ The `req.body` property returns `undefined` when the body has not been parsed. I
 
 In Express 4, the `req.host` function incorrectly stripped off the port number if it was present. In Express 5, the port number is maintained.
 
+<h3 id="req.params">req.params</h3>
+
+Parameters specified as wildcards are represented as arrays of segments:
+
+```js
+app.get('/*splat', (req, res) => {
+  // GET /foo/bar
+  console.dir(req.params)
+  // => [Object: null prototype] { splat: [ 'foo', 'bar' ] }
+})
+```
+
+Optional parameters that are not matched do not have a key in `req.params`. In 4.x an unmatched wildcard would be an empty string and a `:` parameter made optional by `?` had a key with value `undefined`.
+
+The object has null prototype.
+
 <h3 id="req.query">req.query</h3>
 
 The `req.query` property is no longer a writable property and is instead a getter. The default query parser has been changed from "extended" to "simple".

From 50de3edb3d995331f68b85b929070f4cf5b168a4 Mon Sep 17 00:00:00 2001
From: krzysdz <krzysdz@users.noreply.github.com>
Date: Sat, 1 Nov 2025 17:32:04 +0100
Subject: [PATCH 2/6] docs(api-5): document wildcard parameters in req.params

---
 _includes/api/en/5x/req-params.md | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/_includes/api/en/5x/req-params.md b/_includes/api/en/5x/req-params.md
index 2f48c828d4..d68a4f24c5 100644
--- a/_includes/api/en/5x/req-params.md
+++ b/_includes/api/en/5x/req-params.md
@@ -1,6 +1,6 @@
 <h3 id='req.params'>req.params</h3>
 
-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 `{}`.
+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 `Object.create(null)`.
 
 ```js
 // GET /user/tj
@@ -8,6 +8,18 @@ console.dir(req.params.name)
 // => "tj"
 ```
 
+Properties corresponding to wildcard parameters are arrays containing separate path segments split on `/`:
+
+```js
+app.get('/files/*file', (req, res) => {
+  console.dir(req.params.file)
+  // GET /files/note.txt
+  // => [ 'note.txt' ]
+  // GET /files/images/image.png
+  // => [ 'images', 'image.png' ]
+})
+```
+
 When you use a regular expression for the route definition, capture groups are provided in the array using `req.params[n]`, where `n` is the n<sup>th</sup> capture group.
 
 ```js

From 9628fafb30ab6912e24c4c2d82bc1ddb00e6ac31 Mon Sep 17 00:00:00 2001
From: Sebastian Beltran <bjohansebas@gmail.com>
Date: Thu, 18 Dec 2025 18:38:19 -0500
Subject: [PATCH 3/6] docs(migrating-5): update req.params examples for v5
 wildcard syntax

---
 en/guide/migrating-5.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/en/guide/migrating-5.md b/en/guide/migrating-5.md
index faf0e3e1ca..128b4b3b6e 100755
--- a/en/guide/migrating-5.md
+++ b/en/guide/migrating-5.md
@@ -529,6 +529,22 @@ app.get('/*splat', (req, res) => {
 
 Optional parameters that are not matched do not have a key in `req.params`. In 4.x an unmatched wildcard would be an empty string and a `:` parameter made optional by `?` had a key with value `undefined`.
 
+```js
+// v4
+app.get('/:file.:ext?', (req, res) => {
+  // GET /image
+  console.dir(req.params)
+  // => { file: 'image', ext: undefined }
+})
+
+// v5
+app.get('/:file{.:ext}', (req, res) => {
+  // GET /image
+  console.dir(req.params)
+  // => [Object: null prototype] { file: 'image' }
+})
+```
+
 The object has null prototype.
 
 <h3 id="req.query">req.query</h3>

From edf35b5e875452e52ebc2c0a3abe325df49d9396 Mon Sep 17 00:00:00 2001
From: Sebastian Beltran <bjohansebas@gmail.com>
Date: Thu, 18 Dec 2025 20:36:43 -0500
Subject: [PATCH 4/6] docs: apply suggetions

---
 en/guide/migrating-5.md | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/en/guide/migrating-5.md b/en/guide/migrating-5.md
index 1b49794790..ce4465ca32 100755
--- a/en/guide/migrating-5.md
+++ b/en/guide/migrating-5.md
@@ -518,7 +518,11 @@ In Express 4, the `req.host` function incorrectly stripped off the port number i
 
 <h3 id="req.params">req.params</h3>
 
-Parameters specified as wildcards are represented as arrays of segments:
+The `req.params` object now has a **null prototype**. Additionally, there are two important behavioral changes:
+
+**Wildcard parameters are now arrays:**
+
+Wildcards (e.g., `/*splat`) capture path segments as an array instead of a single string.
 
 ```js
 app.get('/*splat', (req, res) => {
@@ -528,17 +532,26 @@ app.get('/*splat', (req, res) => {
 })
 ```
 
-Optional parameters that are not matched do not have a key in `req.params`. In 4.x an unmatched wildcard would be an empty string and a `:` parameter made optional by `?` had a key with value `undefined`.
+**Unmatched parameters are omitted:**
+
+In Express 4, unmatched wildcards were empty strings (`''`) and optional `:` parameters (using `?`) had a key with value `undefined`. In Express 5, unmatched parameters are completely omitted from `req.params`.
 
 ```js
-// v4
+// v4: unmatched wildcard is empty string
+app.get('/*', (req, res) => {
+  // GET /
+  console.dir(req.params)
+  // => { '0': '' }
+})
+
+// v4: unmatched optional param is undefined
 app.get('/:file.:ext?', (req, res) => {
   // GET /image
   console.dir(req.params)
   // => { file: 'image', ext: undefined }
 })
 
-// v5
+// v5: unmatched optional param is omitted
 app.get('/:file{.:ext}', (req, res) => {
   // GET /image
   console.dir(req.params)
@@ -546,8 +559,6 @@ app.get('/:file{.:ext}', (req, res) => {
 })
 ```
 
-The object has null prototype.
-
 <h3 id="req.query">req.query</h3>
 
 The `req.query` property is no longer a writable property and is instead a getter. The default query parser has been changed from "extended" to "simple".

From 80a5f3794075489038951382f9defccc98305798 Mon Sep 17 00:00:00 2001
From: Sebastian Beltran <bjohansebas@gmail.com>
Date: Thu, 18 Dec 2025 20:51:07 -0500
Subject: [PATCH 5/6] docs(migrating-5): clarify req.params behavior with
 string paths and regex

---
 en/guide/migrating-5.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/en/guide/migrating-5.md b/en/guide/migrating-5.md
index ce4465ca32..515856386a 100755
--- a/en/guide/migrating-5.md
+++ b/en/guide/migrating-5.md
@@ -518,7 +518,7 @@ In Express 4, the `req.host` function incorrectly stripped off the port number i
 
 <h3 id="req.params">req.params</h3>
 
-The `req.params` object now has a **null prototype**. Additionally, there are two important behavioral changes:
+The `req.params` object now has a **null prototype** when using string paths. However, if the path is defined with a regular expression, `req.params` remains a standard object with a normal prototype. Additionally, there are two important behavioral changes:
 
 **Wildcard parameters are now arrays:**
 

From b7d13cfeb038c44493697970e534547ff7dc0242 Mon Sep 17 00:00:00 2001
From: Sebastian Beltran <bjohansebas@gmail.com>
Date: Thu, 18 Dec 2025 20:53:19 -0500
Subject: [PATCH 6/6] docs(req.params): clarify default object behavior with
 string paths and regex

---
 _includes/api/en/5x/req-params.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/_includes/api/en/5x/req-params.md b/_includes/api/en/5x/req-params.md
index 9bf2efb70e..4037832cb4 100644
--- a/_includes/api/en/5x/req-params.md
+++ b/_includes/api/en/5x/req-params.md
@@ -1,6 +1,6 @@
 <h3 id='req.params'>req.params</h3>
 
-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 `Object.create(null)`.
+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 `Object.create(null)` when using string paths, but remains a standard object with a normal prototype when the path is defined with a regular expression.
 
 ```js
 // GET /user/tj