📅  最后修改于: 2022-03-11 14:54:55.426000             🧑  作者: Mango
-- convert a string to upper case
local s = 'hello world' s = s:upper()
--> 'HELLO WORLD'
-- convert a string to lower case local s = 'HELLO WORLD'
s = s:lower()
--> 'hello world'