69 lines
2.2 KiB
Markdown
69 lines
2.2 KiB
Markdown
|
---
|
||
|
|
id: custom-validators-sanitizers
|
||
|
|
title: Custom validators/sanitizers
|
||
|
|
---
|
||
|
|
|
||
|
|
Although express-validator offers plenty of handy validators and sanitizers through its underlying
|
||
|
|
dependency [validator.js](https://github.com/chriso/validator.js), it doesn't always suffice when
|
||
|
|
building your application.
|
||
|
|
|
||
|
|
For these cases, you may consider writing a custom validator or a custom sanitizer.
|
||
|
|
|
||
|
|
## Custom validator
|
||
|
|
A custom validator may be implemented by using the chain method [`.custom()`](api-validation-chain.md#customvalidator).
|
||
|
|
It takes a validator function.
|
||
|
|
|
||
|
|
Custom validators may return Promises to indicate an async validation (which will be awaited upon),
|
||
|
|
or `throw` any value/reject a promise to [use a custom error message](feature-error-messages.md#custom-validator-level).
|
||
|
|
|
||
|
|
> **Note:** if your custom validator returns a promise, it must reject to indicate that the field is invalid.
|
||
|
|
|
||
|
|
### Example: checking if e-mail is in use
|
||
|
|
```js
|
||
|
|
const { body } = require('express-validator');
|
||
|
|
|
||
|
|
app.post('/user', body('email').custom(value => {
|
||
|
|
return User.findUserByEmail(value).then(user => {
|
||
|
|
if (user) {
|
||
|
|
return Promise.reject('E-mail already in use');
|
||
|
|
}
|
||
|
|
});
|
||
|
|
}), (req, res) => {
|
||
|
|
// Handle the request
|
||
|
|
});
|
||
|
|
```
|
||
|
|
|
||
|
|
### Example: checking if password confirmation matches password
|
||
|
|
```js
|
||
|
|
const { body } = require('express-validator');
|
||
|
|
|
||
|
|
app.post('/user', body('passwordConfirmation').custom((value, { req }) => {
|
||
|
|
if (value !== req.body.password) {
|
||
|
|
throw new Error('Password confirmation does not match password');
|
||
|
|
}
|
||
|
|
|
||
|
|
// Indicates the success of this synchronous custom validator
|
||
|
|
return true;
|
||
|
|
}), (req, res) => {
|
||
|
|
// Handle the request
|
||
|
|
});
|
||
|
|
```
|
||
|
|
|
||
|
|
## Custom sanitizers
|
||
|
|
Custom sanitizers can be implemented by using the method `.customSanitizer()`, no matter if
|
||
|
|
the [validation chain one](api-validation-chain.md#customsanitizersanitizer) or
|
||
|
|
the [sanitization chain one](api-sanitization-chain.md#customsanitizersanitizer).
|
||
|
|
Just like with the validators, you specify the sanitizer function, which _must_ be synchronous at the
|
||
|
|
moment.
|
||
|
|
|
||
|
|
### Example: converting to MongoDB's ObjectID
|
||
|
|
```js
|
||
|
|
const { param } = require('express-validator');
|
||
|
|
|
||
|
|
app.post('/object/:id', param('id').customSanitizer(value => {
|
||
|
|
return ObjectId(value);
|
||
|
|
}), (req, res) => {
|
||
|
|
// Handle the request
|
||
|
|
});
|
||
|
|
```
|