Validate

A lightweight express middleware to easily validate user input in requests.

import validateMiddleware from 'express-validate-system';

const validationRules = {
	body: {
		email: (email) => ({
			'Please provide an email.': email,
			'Invalid email.': email && email.indexOf('@') !== -1,
		}),
		password: (password) => ({
			'No password provided.': password,
			'Your password is not long enough.': password && password.length > 6,
		}),
	},
};

app.post('/api/users', validateMiddleware(validationRules), (request, response) => {
	// TODO: Create the user here. request.body.email and request.body.password are validated based on the rules in validationRules because of the validateMiddleware.
});

app.use((error, request, response, next) => {
	// The error middleware should handle the response. `error` is a Boom#badRequest error with an array of errorMessages in it's data property.
});

Validation Rules

To validate requests, you need to pass validation rules to the validate middleware. The rules per property are a validator function. A validator function returns an object with one or more error messages as keys and the validation as value where true is valid and false invalid.

For example, the following creates a rule on body.email which validates if the email exists and if it's valid (valid as in an @ exists, this is for demonstration purposes only):

const validationRules = {
	// The scope of the validation rule is request.body. You could just as well validate request.query, if you want.
	body: {
		// We want to validate the email property on the body. We
		// create a validator function which returns an object with
		// multiple error messages and the validation result as
		// value (where true is valid and false is invalid).
		email: (email) => ({
			// Check if the email exists.
			'Please provide your email.': email,
			// Check if the email contains an @ character.
			'Please provide a valid email.': email && email.indexOf('@') !== -1,
		}),
	},
};

Now, if a request with the body { email: null } is parsed, the validate will call the validator function and parse the object. 'Please provide your email.': email, will be false and thus email is considered invalid. validate will continue parsing all validation rules. 'Please provide a valid email.': email && email.indexOf('@') !== -1, will also be false and thus again invalid.

Nested Rules

You can also nest validation rules. This makes it easier to validate nested properties. The below snippet creates a validate rule for request.body.address.streetName and request.body.address.postalCode:

const validationRules = {
	body: {
		address: {
			streetName: (streetName) => ({
				'Please fill in your street.': streetName,
			}),
			postalCode: (postalCode) => ({
				'Please fill in your postal code.': postalCode,
			}),
		},
	},
};

Arrays

You can also validate all items in an array.

const validationRules = {
	body: {
		list: [{
			name: (name) => ({
				'Name should be set': name,
			}),
		}],
		'list.length': (length) => ({
			'There should be 3 items in the list.': length === 3,
		}),
	}
}

The will also check the length of the list in request's body. You can use the dot notation to check specific properties.

References

You can also reference other properties. The validator function's arguments contain all parent objects up to the root object (the request).

const validationRules = {
	body: {
		value: (value) => ({
			'Value must be bigger than 42.': value > 42,
		}),
		otherValue: (otherValue, body, request) => ({
			'The other value should be smaller than value.': otherValue < body.value,
		}),
	},
};

Custom errors

Since version 2.0 this library passes Boom errors to the next callback. To create your own errors, pass a callback to the validateMiddleware which creates error messages.

const middleware = validateMiddleware({
	body: {
		test: (test) => ({
			'Test should be set to 123.': test === 123,
		}),
	},
}, (errorMessages) => new Error('This is my custom error.'));

Validate

You can also use the validate function directly without using the middleware. Pass the validation rules to validate and it returns an array with one or more error messages.

import { validate } from 'express-validate-system';

const errorMessages = validate(validationRules);