Unobtrusive JavaScript (separation of markup and behavior)
Back in the days, it was common to put your click handler inside the markup. Now it's recommended that you do not write your JS code inside your markup but include it via DOM events.
Progressive enhancement
User gets better experience if they are using standards compliant browser and/or has JavaScript enabled. Website/web application is still accessible even if they have older browser or has JS disabled.
Feature detection and not browser detection
Keeping above points aside, I would really focus on conveying the message (breaking the pre-conceived notion) that JavaScript is a toy language. I have seen too many developers who thinks this way and everything is downhill from there. You need to explain them how JavaScript is a very powerful language and why they need a JS library (because of browser inconsistencies) even though JS itself is very powerful.
Good luck.
