Safeguarding Your Backend API: A Comprehensive Guide to Input Validation with Validatorjs
The Importance of Input Validation
When building a backend API, one of the most critical tasks is ensuring the integrity of user input data. You can’t always trust user input, and that’s why adding an extra layer of validation is crucial. In this article, we’ll explore the power of Validatorjs, a popular validation library inspired by Laravel’s validator, and how it simplifies data validation in JavaScript.
Getting Started with Validatorjs
To begin, let’s initialize our project directory with the necessary dependencies, including Express, body-parser, mongoose, morgan, Validatorjs, and Bcryptjs. We’ll also install Nodemon as a dev dependency.
Basic Input Validation with Validatorjs
Validatorjs provides a Validator constructor function that takes three arguments: data, rules, and customErrorMessages. To demonstrate basic input validation, we’ll create a simple validation middleware to validate user inputs on signup.
Creating a Validation Middleware
We’ll update the validate.js file inside the helper folder to initialize the Validatorjs package in AMD format. This approach simplifies our code when writing multiple validation middlewares. Next, we’ll define a signup function that contains our validation rules and the validator higher-order function.
Understanding Validation Rules
Let’s break down the validation rules used in our example:
required: The field must have a length greater than zero.string: The field must be a string.email: The field must be in an email format (e.g., [email protected]).min:6: The field string length must be greater than or equal to six.confirmed: The field must have a matching field with matching values, commonly used for password confirmation fields.
Advanced Validation Rules with Validatorjs
In this section, we’ll explore how to write custom validation rules for two use cases: implementing strict password policies and checking if the email/username attribute already exists in the database.
Implementing Strict Password Policies
We’ll update the validate.js file to use regex to validate incoming values for an input field with the strict validation rule.
Checking for Existing Email/Username Attributes
To check if the email or username attribute already exists, we’ll make an asynchronous call to our database using Validator.registerAsync(). This allows us to make a non-blocking call to our database while validating other fields simultaneously.
Putting it All Together
By following this tutorial, you’ve learned how to implement basic input validation with Validatorjs and define custom validation rules for specific use cases. Validatorjs offers more predefined rules than covered in this tutorial, so be sure to explore its capabilities further.
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