A difficult and challenging task I had been given is to use the JQuery validate.js to validate the date fields, but this was then split out into 3 fields. One for day, month and of course year, which sounds easy, but it was not. The issue comes that validate.js is built to validate one field on its own and we wanted to validate not just each field, but also as a whole date.
This libraries purpose is to automatically inject the necessary tags and commands to the users mark-up, so that it meets the standards as much as possible. There are also commands for the users to inject the methods on to specific parts if the library does not get them automatically. Also the automatic functionality can be turned off if only partly needed.
I see a lot of companies rush, rush, rush and push, push, push to get things in fast. They want to deliver new features every second if they could. However this has big risk and future problems they keep coming. I always say Prepare for the Worst and Hope for the Best!