Have you ever tried to develop forms? Or wrote a script for the validation of these forms on the client side? Did you have to use the already existing plugins for form validation?
I had to, but I've never been 100% satisfied with any approach to neither solving the problem directly (own validation script for each project under its forms), nor how the existing third-party plugins works.
The main problems of own scripts and plug-ins have always been - the flexibility, convenience and simplicity.
A large number of data-attributes, required for configuration scripts (as in Parsley.js) makes the code less readable, and never remembers how to write them correctly. Not so simple ...
Not all plugins are well suited for the desired HTML-forms, and constantly write own scripts for different forms are not always convenient and reasonable.
Create something flexible, easily configurable, a fully controllable, with an intuitive syntax and the main idea - to validate.
The solution resulted in a small opensorce plugin, called tFormer.js.