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docs: clarify req.params type and usage with regular expressions #2101

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docs: clarify req.params type and usage with regular expressions #2101

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6 changes: 4 additions & 2 deletions _includes/api/en/4x/req-params.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,14 +8,16 @@ console.dir(req.params.name)
// => 'tj'
```

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

```js
// GET /file/javascripts/jquery.js
console.dir(req.params[0])
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.
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6 changes: 4 additions & 2 deletions _includes/api/en/5x/req-params.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,16 +8,18 @@ console.dir(req.params.name)
// => "tj"
```

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.
When you use a regular expression for the route definition, capture groups are provided as integer string keys using `req.params['n']`, where `n` is the n<sup>th</sup> capture group.

```js
app.use(/^\/file\/(.*)$/, (req, res) => {
// GET /file/javascripts/jquery.js
console.dir(req.params[0])
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 }}/5x/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.
Expand Down