Install Emacs on Mac OSX with brew

$ brew cask install emacs
Reference: https://www.gnu.org/software/emacs/download.html#macos

If you run into this error while access Desktop/Documents/Downlaods directory:


Here is the fix:

indent with 4 spaces in Emacs json-mode

1. install json-mode with

M-x package-install RET json-mode RET

2. set indent with:

M-x customize-group RET json-mode RET

Then change the default number from '2' to '4'.