:let g:var_name = 1

buffer-variable    b:    Local to the current buffer.
window-variable    w:    Local to the current window.
tabpage-variable   t:    Local to the current tab page.
global-variable    g:    Global.
local-variable     l:    Local to a function.
script-variable    s:    Local to a |:source|'ed Vim script.
function-argument  a:    Function argument (only inside a function).
vim-variable       v:    Global, predefined by Vim.

let g:var_name = 1

let g:javascript_conceal = 1

autocmd Filetype javascript let b:javascript_fold = 1