It's possible to write your own form validations, but with so many jQuery plugins available to do it for you, it's often a lot easier, simpler, and most importantly, quicker, to use a plugin to perform your validations. All of these plugins are lightweight, easy to use, and of course, will allow you add validations to your forms and save time when working on any of your projects.
1. jQuery Validation Plugin
This plugin can be used to add validation rules to any of your jQuery forms. It's lightweight and can be customized easily!
Bootstrap Validator is a simple form validator plugin designed especially for the Bootstrap framework. If your site uses Bootstrap, this is a great option to use for form validation.
Smoke is another form validation plugin that's meant to be used with Bootstrap. Some of its great features include support for Angular and Bootstrap's date-picker.
The Validatr plugin is unique in that it uses HTML5 input attributes to perform validation, which makes it super lightweight.
Validetta is a sef-proclaimed "tiny" plugin that can be used to perform client-side validations. If you're looking for a lightweight, simple jQuery plugin, this is a good option.
The jQuery Ketchup plugin for form validation is great because it's built as a validation framework that can be completely customized to meet your needs. If you want a good jumping off point for making your own customizations and validation rules, Ketchup may be the way to go.