Default key-chord mode in Prelude

Today I read the source codes of Prelude, except for knowing some new global key bindings, the most interesting one is the key-chord mode. Maybe I came from vi, so the double pressing key is familiar for me. And I enjoy that a lot. So I write down it as a note for its usage. :P
Predlude set key-chord mode enabled by default, of course it can be turned off by:

(key-chord-mode -1)

This piece of code can be added to the custom.el file, which is the personal configure file for Prelude. In that case, evil-mode maybe used to mixture some operations with vi, while I never tried it. Below are the shortcuts and commands in key-chord mode:

jj+`c`      jump to a word starts with a character
jl+`c`      jump to a line marked with a letter
jk+`c`      jump to a word contains a letter
JJ          switch to the previous buffer
uu          open the undo-tree

ps: I updated the key-chord mode by add a new command in my custom.el:

(key-chord-define-global "kk" 'prelude-kill-whole-line)

Maybe that needs some tests for several days, I will post any update by then.