if Statement

if / elseif / else

if condition then
    # body
elseif otherCondition then
    # body
else
    # body
end

The then keyword is required after each condition. The block is closed with end. The elseif and else clauses are optional, and any number of elseif clauses may appear.

elseif vs else if

The elseif and else if constructs are semantically different.

elseif (one word) is part of a single if statement and requires one end:

if score >= 90 then
    grade = "A"
elseif score >= 80 then
    grade = "B"
else
    grade = "F"
end

else if (two words) creates a nested if inside an else block. Each if requires its own end:

if score >= 90 then
    grade = "A"
else
    if score >= 80 then
        grade = "B"
    else
        grade = "F"
    end       # closes inner if
end           # closes outer if

With elseif, the next condition is evaluated immediately. With else if, statements can run between the else and the nested if:

if Data.source == "api" then
    Data.result = handleApi()
else
    var fallback = Data.cache ?? loadDefaults()
    if fallback is not null then
        Data.result = fallback
    else
        fail "No data available"
    end
end

This would not be possible with elseif, because there is no place to put the var fallback line. Use elseif for straightforward conditional chains, and else if when you need to do work before the nested condition.