$ env
SHELL=/bin/bash
EDITOR=vim
TERM=xterm
HOME=/Users/ed
GOPATH=/Users/ed/go
FOO=fooming_at_the_mouth
BAR=bar_snacks

$ json_env -f json -v BAR -v FOO
{"BAR":"bar_snacks","FOO":"fooming_at_the_mouth"}

$ json_env -f js -v EDITOR
window.ENV = {"EDITOR":"vim"};

$ json_env -f js -e SHELL -e EDITOR -e TERM -e HOME -e GOPATH
window.ENV = {"FOO":"fooming_at_the_mouth","BAR":"bar_snacks"};