How to enable code folding?

[heisian]

• I see JavaScriptFold() in the source, however vim tells me No fold found when I type zc in a foldable block
• If I add the following manually to my ~/.vimrc, it seems to work:

" From vim-es6 source:
setl foldmethod=syntax
setl foldlevelstart=1
syntax region foldBraces start=/{/ end=/}/ transparent fold keepend extend

• How can I get folding to work without manually adding the above to ~/.vimrc?