How to get user's email once they connect on my website with Facebook?

I have set up registration through FB on my website. Unfortunately, I am unle开发者_开发百科arned in javascript and am having trouble using this information. The registration gets the user's name and email. I would like to use their email address to pre-fill a form I use later in the website. Am I able to do this with their registration information? Thanks a ton.

You won't be able to access it via javascript. Facebook will send you a signed_request http post parameter and you will need to decode it with server side code as detailed here in the section entitled "reading the data".