LUA isn't strictly typed, and doesn't have a built-in mechanism for type checking paramaters and variables.
Sometimes, though, we need to check that a value is of a given type - a LUA component of a WAF might, for example, want to check that a specific query-string argument is numeric
This snippet focuses solely on that use-case - checking that a variable/string is numeric in format
function is_numeric(x)
if tonumber(x) ~= nil then
return true
end
return false
end
vals = {"1234","abcd",'1a','1.1'}
for _,v in pairs(vals) do
if is_numeric(v) then
print("Yes - " .. v)
else
print("No - " .. v)
end
end
-- Output:
-- Yes - 1234
-- No - abcd
-- No - 1a
-- Yes - 1.1