# express-html-validator
[](https://github.com/rooseveltframework/express-html-validator/actions?query=workflow%3ACI) [](https://www.npmjs.com/package/express-html-validator)
A [middleware](https://expressjs.com/en/guide/using-middleware.html) for the [Express framework](https://expressjs.com) that automatically validates the HTML on all your [Express routes](https://expressjs.com/en/guide/routing.html), powered by [html-validate](https://html-validate.org/). This module was built and is maintained by the [Roosevelt web framework](https://github.com/rooseveltframework/roosevelt) [team](https://github.com/orgs/rooseveltframework/people), but it can be used independently of Roosevelt as well.
## Usage
First declare `express-html-validator` as a dependency in your app.
Then require the package into your application and call its constructor, passing along your Express app:
```js
const express = require('express')
const expressValidator = require('express-html-validator')
const app = express()
const config = {}
// Generally this would be used in development mode
if (process.env.NODE_ENV === 'development') {
expressValidator(app, config)
}
// expressValidator should be called before defining routes
app.get('/', (req, res) => {
// This html response will be validated in real time as it's sent
res.sendFile(path.join(publicDir, 'index.html'))
})
```
You can also run the validator on arbitrary strings outside of the Express context:
```js
const config = {}
const expressValidator = require('express-html-validator')(config)
const someHtml = `
Some HTML that will not validate
hello world
`
const validationResult = expressValidator(someHtml)
```
Since the example HTML is not valid, if you display the contents of `validationResult` in a browser, you will see validation errors.
## Configuration
Optionally you can pass this module a set of configs:
- `exceptions`: A set of params that can be used to prevent validation in certain scenarios:
- `routes` *[Array]*: An array of routes to exclude from validation. Supports wildcard `*` syntax.
- Default: `[]`.
- `header` *[String]*: A custom header that when set will disable the validator on a per request basis.
- Default: `'Partial'`.
- `modelValue` *[String]*: An entry in your data model passed along with a `res.render` that when set will disable validation on the rendered HTML.
- Default: `'_disableValidator'`
- `validatorConfig` *[Object]*: [html-validate configuration](https://html-validate.org/usage/#configuration) that determines what errors the validator looks for.
- Note: The full list of available validator rules can be found [here](https://html-validate.org/rules/).
- Note: This configuration can also be set by a `.htmlValidate.json` file placed in your app root directory.
- Default:
```json
{
"extends": ["html-validate:standard"]
}
```