> For the complete documentation index, see [llms.txt](https://iamthilina.gitbook.io/xpress-req-validator/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://iamthilina.gitbook.io/xpress-req-validator/background-story.md).

# Background Story

Request validation is a must when developing an API. Express allows following options to achieve this.

1. Handling validation logic in each route handler (method-1)

```javascript
router.post('/device/data', (req, res) => {
        const {deviceID, serialNo} = req.body;
        if(!deviceID || !serialNo) {
            const err = new Error('invalid parameters')
            res.status(400).json({err})
        }

        controller(req.body) // controller section
}
```

    2\. writing a separate middleware in each route handler (method-2)

```javascript
router.post('/device/data', deviceDataValidationMiddleware, (req, res) => {
        controller(req.body) // controller section
}
```

Method-1 is an ugly and painful way of achieving request validation. Method-2 is comparatively better, but still requires you to write a ton of middleware. Both methods demand a significant effort to unit test the route handler.

There has to be a better way of validating requests with less unit testing effort and of course by separating the concerns. `xpress-req-validator` is the solution. It allows developers to define all their request validation specs in a single place, make route handling code snippets much cleaner and finally reducing the unit test effort