`apt install -y lua-cjson` 安装

编辑 tmp.lua

cjson = require "cjson"
p = 666
d = "23.42"
payload='{"d":[{"pres":'..(p)..',"temp":"'..(d)..'"}]}'
print("payload = " .. payload)

j = cjson.decode(payload)
print("payload.d[1].temp = ".. j.d[1].temp)

`lua tmp.lua` 运行结果：

payload = {"d":[{"pres":666,"temp":"23.42"}]}
payload.d[1].temp = 23.42

很显然，支持 json 嵌套

lua-cjson 手册可参考这里：

https://kyne.au/%7Emark/software/lua-cjson-manual.html