Introduction

What's v8n?

v8n aims to be the most fluent and simple validation library for use in any context. The API is beautifully readable and allows for easy creation of complex validations in any part of your app. Even though there are many useful default validation methods, it's a breeze to add your own fluent rules to v8n and use them anywhere in your app.

The name v8n is actually derived from the structure of the word "validation". If you look closely you will find that between the v and the n in there are precisely 8 letters (a l i d a t i o). So we get from the sort of boring word validation to the very nice looking acronym v8n.

Features

• Fluent and chainable API
• Useful standard validation rules (30+)
• Custom validations rules
• Asynchronous validation
• Reusability
• TypeScript support

Getting started

Using v8n is supposed to be easy and intuitive. Aside from usage in the browser with versions hosted on popular CDN services, you can import the library into your codebase with import or require depending on how bleeding-edge you are.

The example below shows one way to get started. Simply create an .html file and add this to it. Now you will be able to use v8n() anywhere on that page right away.

<script src="https://unpkg.com/v8n/dist/v8n.min.js"></script>

This is just the most straightforward approach without any build setup or complex imports. The Installation page gives you an overview of all the available installation methods.

After you've included v8n in some way you can use it very easily.

v8n()
  .string()
  .test('My string!'); //true

Overview

Fluent API

One of the main goals of v8n is its simple and fluent usage. You simply chain your rules and build even incredibly complex rules with easy. You can chain any number of built-in rules and even combine them with your own custom rules in the same way. Make sure to check out all the built-in rules and how you can add your own.

v8n()
  .string()
  .first('H')
  .last('o')
  .test('Hello'); //true

The code above simply validates that the given value is a string, it's first character is H and the last is o. Doesn't that look really readable? Be sure to read up on validation strategies after you wrote your validations, so that you can leverage them to their full extent.

TypeScript support

The v8n library comes with TypeScript support built in. When you import v8n in a TypeScript project, you will get full autocompletion and type support. This support also works in any other environments if your code editor supports it. This means that intellisense works in everywhere, including places without any module loaders (like browsers importing the script from a CDN).

Custom rules

Extending is at the core of v8n. And it's easy, too. All you do is pack your own validation into a function that returns a boolean. You can do as much logic in your rule as you like, all that matters is the boolean return and you're good to go. Once you created your function just add it using extend(). Take a look at the Extending page for more details and different types of rules you might want to add.

::: tip You can also create Promise based validation rules. :::

Validation strategies

Sometimes you might not want a boolean return, maybe you're working in a try-catch or you need to know which rules failed for the given value. You're in luck, v8n offers multiple validation strategies that give you great flexibility when writing your code and give your more than just true or false. If you want to know more read up about all the validation strategies and how to use them.