How to check in Lua if there are multiple elements in a table?

I made a program, which checks if in table has (for example) "A" and a "B" in itself. But it doesn't works.

Here's code:

function inTable(t,e)
    return t[e] ~= nil
end

--Example
local table_ = {"A","B"}

if inTable(table_,"A") and inTable(table_,"B") then
    --Do some stuff
end

Please, help me.

I tried everything but it still doesn't work.

You are checking if those exist as keys. You should be checking if they exist as values. You can change the function to this

function inTable(t,e)
    for k,v in pairs(t) do
        if v == e then
            return true
        end
    end
    return false
end

Also, in case you didn't know

local table_ = {"A","B"}

is equivalent to

local table_ = {[1] = "A", [2] = "B"}