There is json.decode - I think a built in json.encode would be useful and logical.
There are other already made ways to do it but I think if json.decode exists so should json.encode for turning a lua table into JSON as a part of core api.
http://regex.info/blog/lua/json
http://lua-users.org/wiki/JsonModules
A json.encode would be great, I was surprised there is only a decode
@Pkeod Thanks for the Gist, I’m using it in my project now and it seems to work well.
I’m using this one now
is there a reason why json.encode() is not available in the official API? 
Yes, a semi vague reason. Should an empty table encode to a JSON object {} or an array []?
This is my goto solution for json.encode: https://github.com/rxi/json.lua