JS Test Foldexpr

function! JST_Folds(lnum)
  let line = getline(a:lnum)
  if line =~ '^describe'
    return '>1'
  elseif line =~ '^\s\+\(describe\|it\)'
    return 'a1'
  elseif line =~ '^\s*}\s*)\s*;'
    return 's1'
  else
    return '='
  endif
endfunction

set fdm=expr
set fde=JST_Folds(v:lnum)