Sanitization Chain API

The sanitization chain is a middleware, and it should be passed to an Express route handler.

You can add as many sanitizers to a chain as you need. When the middleware runs, it will modify each field in place, applying each of the sanitizers in the order they were specified:

const { body } = require('express-validator');
app.get('/', body('trimMe').trim(), (req, res, next) => {
  // If req.body.trimMe was originally "  something ",
  // its sanitized value will be "something"
  console.log(req.body.trimMe);
});

Standard sanitizers

All sanitizers listed by validator.js are made available within a Sanitization Chain, and are called "standard sanitizers" in express-validator.

This means you can use any of those methods, e.g. normalizeEmail, trim, toInt, etc.

For a complete list of standard sanitizers and their options, please check validator.js' docs.

Note: Since validator.js only accepts string as input, any value (including arrays and objects) that needs to be sanitized by a Standard Sanitizer is first converted to such type.

Additional methods

In addition to the standard sanitizers, the following methods are also available within a Sanitization Chain:

.customSanitizer(sanitizer)

• sanitizer(value, { req, location, path }): the custom sanitizer function. Receives the value of the field being sanitized, as well as the express request, the location and the field path.

Returns: the current sanitization chain instance

Adds a custom sanitizer to the current sanitization chain. It must synchronously return the new value.

Example:

const { param } = require('express-validator');
app.get(
  '/object/:id',
  param('id').customSanitizer((value, { req }) => {
    return req.query.type === 'user' ? ObjectId(value) : Number(value);
  }),
  objectHandler,
);

.default(default_value)

Returns: the current sanitization chain instance

Replaces the current value with a default one if the current value is included in ['', null, undefined, NaN].

app.post('/', body('username').default('foo'), (req, res, next) => {
  // 'bar'     => 'bar'
  // ''        => 'foo'
  // undefined => 'foo'
  // null      => 'foo'
  // NaN       => 'foo'
});

.replace(values_to_replace, new_value)

Returns: the current sanitization chain instance

Replaces the current value with a new one if the current value is included in a given Array.

app.post('/', body('username').replace(['bar', 'BAR'], 'foo'), (req, res, next) => {
  // 'bar_' => 'bar_'
  // 'bar'  => 'foo'
  // 'BAR'  => 'foo'
  console.log(req.body.username);
});

.run(req)

Returns: a promise that resolves when the sanitization chain ran.

Runs the current sanitization chain in an imperative way.

const { check } = require('express-validator');
app.post('/create-post', async (req, res, next) => {
  // BEFORE:
  // req.body.content = ' hey your forum is amazing! <script>runEvilFunction();</script>    ';
  await check('content').escape().trim().run(req);

  // AFTER:
  // req.body.content = 'hey your forum is amazing! &lt;script&gt;runEvilFunction();&lt;/script&gt;';
});

.toArray()

Returns: the current sanitization chain instance

Converts the value to an array. undefined will result in an empty array.

app.post('/', [body('checkboxes').toArray()], (req, res, next) => {
  // ['foo', 'bar]  => ['foo', 'bar']
  // 'foo'          => ['foo']
  // undefined      => []
  console.log(req.body.checkboxes);
});

.toLowerCase()

Returns: the current sanitization chain instance

Converts the value to lower case. Non string value will return itself.

app.post('/', [body('username').toLowerCase()], (req, res, next) => {
  // 'Foo'      => 'foo'
  // undefined  => undefined
  // null       => null
  console.log(req.body.username);
});

.toUpperCase()

Returns: the current sanitization chain instance

Converts the value to upper case. Non string value will return itself.

app.post('/', [body('username').toUpperCase()], (req, res, next) => {
  // 'Foo'      => 'FOO'
  // undefined  => undefined
  // null       => null
  console.log(req.body.username);
});