Jump to contents page with epub.js

A user can upload a epub file which, after the user provides a few options (like whether they want it rendered continuous or not) I open and display with epub.js. Together with the epub in the web page I provide a few buttons that allow the user to do things like page forwards and backwards through the epub.

I was wondering how I could have a button which changes the location to the contents page for the epub. Searching tells me that I can jump to a page using

book.goto(some_cfi)

or

rendition.display(some_cfi)

but I’m not sure what a cfi is nor if there’s any way for epub.js to know the cfi for the contents page (if it even exists) is nor can I currently get it to do anything.

How can I create a button that jumps to the contents page in a epub file display with epub.js?