PhoneGap is not a language. It has some requirements as to folder structure and config.xml, but that's not the same thing as a coding standard.
You'll be using ES5+, HTML, and CSS. Code accordingly. If you aren't familiar with those languages yet, start there first. You'll also be interfacing heavily with the Browser's Document Object Model (DOM), so make sure you're familiar with that as well, and how to avoid performance gotchas when working with the DOM.