Lua json解析字段不存在处理方式

#!/usr/bin/lua local cjson = require "cjson" local data = {} --local response = "{\"opt\":\"1\",\"auth_mode\":\"4\",\"account\":\"15067191032\"}" local response = "{\"opt\":\"1\"}" data=(response) local op = data["opt"] local auth_mode = (data["auth_mode"] == nil and 0 or data["auth_mode"]) local account = (data["account"] == nil and "N/A" or data["account"]) print("op : " ..op.. ", auth_mode : " ..auth_mode.. ", account : " ..account)