How to Validate Data Using Validator.js?

In every website of today’s world, the most common and useful requirement is to validate data that is passed as input by the user. Whether it’s filling out a form to create a new account or logging in to your old account, data validation is a must. We can never just rely on a user that will surely enter the correct input. We have to be extra careful on our side to make sure the user has entered the correct input, or else notify the user about the correct form of input. The most helpful tool available for browsers and nodes is validator.js. We will now discuss what is validator.js, and how you can validate data using validator.js.

What is Validator.js?

Validato.js is a data validation module. It is a npm module that is inspired by the Laravel framework’s validator. It is a library that allows different types of validation methods to be used in your JavaScript. The main advantage of using validator.js is that it can be used in both browser and node side. It easily allows you to validate data that is entered by the user as input, avoiding any further processing errors that can be caused by bad input.

Let’s see which are the major advantages of using Validator.js:

• It works for both browser and node.
• The standardized and easily readable validation rules.
• ES6 support.
• Error messages in multiple languages.
• Common JS support

How to Install Validator.js Module?

Validator.js is a npm module and you can install it through any of the below mentioned ways.

• Enter the code below to install it using npm

npm install validatorjs

• Code to install it using yarn

yarn add validatorjs

• Enter the code below to install it using bower

$ bower install validaator-js

You can import the validator.js in various platforms as below:

• In browser side:

<script src=”validator.js”></script>

• For Node.js for ES5 support:

let Validator = require(‘validator.js’);

• In Node.js for ES6 support:

Import * as Validator from ‘validatorjs’;

How to Validate Data Using Validator.js?

You can use the validator module to validate your data by the following below syntax:

Let validate= new Validator(data, rules [,customErrorMessages])

In the above code, validate is used as a variable name to point out the newly created validator. data refers to the data which is to be validated. Validation is the set of rules that you want the validator to follow. customErrormessages is an optional parameter that can be used if you want to display a custom message if the user enters bad input.

Example: Enter the code below to check if the entered name is correct and age is above 18.

let validate= new Validator({ name: ‘Man’, age:22},{name:’size:3’, age:’min:18’});

Here, in the above code, as stated the first curly bracket consists of the data that is to be validated consisting of the name and age. The second set of curly brackets consist of the rules that should be followed. Don’t worry ‘size:3’ and ‘min:18’ are called validation rules, that we are going to study below. We have not included any custom error messages for now. We will also discuss below different types of error messages to return.

Which are the Different Validation Rules?

Here we have listed various validation rules along with the form of input in order to pass the test and use of each rule.

Validation rule	Condition for field value to pass the validation test	Usage
accepted	Value must be yes, on, 1 or True	For ‘Terms and service” checkbox
after:date	Value must have date after given date	For date of birth
alpha	Value must contain only alphabets	For any type of name field
alpha-num	Value must have alpha-numeric characters	For password with only alpha-numeric characters
date	Value must be a JavaScript Date object	For any kind of date field
digits:value	Value must be numeric and should have exact length of ‘value’	For mobile number
email	Value must be in email format	For e-mail address field
integer	Value must be in integer format	For field requiring only numbers
in	Value must be in given list of value	For drop down menu
required	Value must not be null or field must not be empty	For fields which are compulsory to have a value
size:value	Value must have size equal to stated “value”	For fields requiring specific length of input
url	Value must be in url format	For url fields
min:value	Value must be greater than stated “value”	For age related fields
max:value	Value must be less than stated “value”	For maximum number of characters
confirmed	The two mentioned fields should have same value	In fields like password and confirm password

How to Register Custom Validation Rules?

You can easily register your own validation rule with a specified name that you can use in place of that name using the code given below:

Validator.register(rule_name, validity_function, custom_errormessage)

Here,

rule_name: The name of the rule that you will use later

validity_function: The function that will check if the input value is correct and return true if so, otherwise False

custom_errormessage: The custom error message that you want to display.

Which are the Ways to Display Error Messages When Validation Fails?

Once a particular field fails to pass the validation test, our next step is to return an error message which can be customized or using the inbuilt error instances in errors property object. The various methods and properties on errors property object are:

• .first(attribute): returns the first error message for given attribute
• .get(attribute):returns the array of error messages of given attribute
• .all():returns an object containing all error messages for all failing attributes
• .errorcount: The total number of error messages.

Example: enter the code below to get first error message if email is wrong.

let validate= new Validator(input, rules);
validate.passes();
validate.fails();
validate.errors.get(‘email’)

Here, if the validation of email attribute fails, then it will return the first error message of email attribute.

In above example, validate.passes() returns true if the result passes and validate.fails() returns true if result fails and false otherwise.

Conclusion

Validation.js can act as a very important tool in your web development part, where you require to test whether the input by your user is of the required processing format or not. I hope the above article has enhanced your knowledge regarding what validator.js is and how to validate data.

Which feature of validator.js attracts you the most? Do tell us in comments below!!