# Routing

The app will search for the first matching route in the order you define, so define error routes last

```javascript
// wiki.js - Wiki route module.
var express = require('express');
var router = express.Router();
router.get('/', function (req, res) {
  res.send('Wiki home page');
})
module.exports = router;

//in app.js
var wiki = require('./wiki.js');
// ...
app.use('/wiki', wiki);
```

## Router Methods

#### Methods

* router.get
* post, put, delete, options

#### Callback

Must respond or call next

### Post

To access post data as json you need `app.use(express.json())`

To access post data you need `app.use(express.urlencoded())`

```javascript
app.post('/form', (req, res) => {
  const name = req.body.name
})
```

## Routes

Can use regex

#### Parameters

```javascript
app.get('/users/:userId/books/:bookId', function (req, res) {
  // Access userId via: req.params.userId
  // Access bookId via: req.params.bookId
  res.send(req.params);
})
```

## Static

```javascript
app.use(express.static('public')); 
app.use(express.static('files'));
```

Now `http://localhost:3000/images/kitten.jpg` will go to directory of `public/images/kitten.jpg`

Will search through folders in order declared returning first match

directory from where you launch your `node`process. If you run the express app from another directory, it’s safer to use the absolute path of the directory that you want to serve:

```javascript
app.use('/static', express.static(path.join(__dirname, 'public')))
```

## Error Handling

Just copied from templates

```javascript
const createError = require("http-errors");

//........
// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get("env") === "development" ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.send("error");
});
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://openai.gitbook.io/code-cheatsheets/js/all/node/routing.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.