Lua Control Flow Guide — if, elseif, and Conditional Logic

In this tutorial, you will learn about Lua Control Flow Guide. We cover key concepts, practical examples, and best practices to help you master this topic.

Lua control flow uses the if keyword followed by a condition, then optionally elseif and else branches, all terminated with end -- supporting comparison operators and logical combinations for complex branching logic.

Basic if Statement

local score = 85

if score >= 60 then
    print("Passed")
end

if-else

local age = 17

if age >= 18 then
    print("Adult")
else
    print("Minor")
end

if-elseif-else

local grade = 75

if grade >= 90 then
    print("A")
elseif grade >= 80 then
    print("B")
elseif grade >= 70 then
    print("C")
elseif grade >= 60 then
    print("D")
else
    print("F")
end

Nested Conditions

local user = { role = "admin", active = true }

if user.active then
    if user.role == "admin" then
        print("Full access granted")
    elseif user.role == "editor" then
        print("Edit access granted")
    else
        print("Read-only access")
    end
else
    print("Account disabled")
end

Comparison Operators

-- Relational
print(5 == 5)    --> true
print(5 ~= 5)    --> false (not equal)
print(5 < 10)    --> true
print(5 <= 5)    --> true
print(10 > 5)    --> true
print(10 >= 5)   --> true

-- String comparison (lexicographic)
print("apple" < "banana")  --> true

Common Mistakes

1. Using = instead of ==

= is assignment, == is equality. if x = 5 then is a syntax error.

2. Forgetting then

Every if and elseif must have then before the body.

3. Missing end

Every if block must close with end. Forgetting end is a common syntax error.

4. Using else if instead of elseif

Lua uses elseif (one word). else if creates a nested if that needs its own end.

Practice Questions

1. What keyword closes an if block? end. Every if must have a matching end.

2. How do you write multi-branch conditions? Use elseif (one word) between if and else: if a then ... elseif b then ... else ... end.

3. What is the difference between = and ==? = assigns a value. == compares two values for equality.

FAQ

{{< faq question="Can I have multiple elseif branches?" >}} Yes, there is no limit. Lua evaluates each elseif in order and executes the first true branch. {{< /faq >}}

{{< faq question="Does Lua have a switch statement?" >}} No built-in switch. Use if-elseif chains. For many cases, consider a table lookup or function dispatch table. {{< /faq >}}

{{< faq question="How do I write a single-line if?" >}} Lua doesn't have a single-line if. Use the and-or idiom: condition and value1 or value2 as a ternary alternative. {{< /faq >}}

What's Next

Now learn about loops in Lua.