Hey there! :)
I can definitely understand the need for a cart checkout plugin to be working correctly! I'd be happy to help resolve the remaining issues with your Chrome extension--after all, Chrome extensions are pretty much just mini web apps under the hood, and web apps tend to be my specialty, especially when they are as JavaScript centric as yours seems to be.
As for the standard "about me" formalities, I've been using JavaScript both professionally and as a hobby most of my life, and while I've only recently joined Freelancer.com, I've been freelancing as a JavaScript expert for quite some time now. By all means, feel free to check my profile for a few testimonials from past clients, as well as to get to know a bit more about me.
With that out of the way, I'd love to hear from you as soon as possible. Toss me a reply so we can get started right away! I look forward to working with you. :)