Input field validation is one of the toughest subjects to breach. This requires a lot of custom code based on your requirements for passwords, email addresses, shipping addresses, or anything else on your checkout page.
The jQuery Form Validator plugin is totally free and one of the best you can use. It’s hosted for free on npm, Bower, and of course GitHub.
For example, you might pass data-validation-length=”6″ onto your password input to force passwords of at least 6 characters or more.
Just note this plugin has a lot of features to work through. You can find full documentation on the homepage using the side navigation to browse through different settings.
You can also find the entire library on CDNJS if you wanna test this out locally or in a browser IDE like CodePen.