Control Flow

If / Else / Else If

Conditional execution works as expected, and conditions can be chained with else if:

let score = 75
 
if (score >= 90) {
    print("A")
} else if (score >= 70) {
    print("B")
} else {
    print("C")
}
// Output: B

For simple value selection, the ternary operator is often more concise.

For Loops

Iterate over arrays using the for ... in syntax:

let numbers = [1, 2, 3, 4]
 
for (n in numbers) {
    print(n * 2)
}

While Loops

Execute a block of code repeatedly while a condition is true:

let i = 0
let sum = 0
while (i < 5) {
    sum += i
    i++
}
print(sum)  // Output: 10

Safety Note: While loops are protected by the operation limit. If a loop runs for too many iterations, execution will be terminated to prevent infinite loops. See Security for more details.

Break & Continue

Inside for and while loops, break exits the loop immediately and continue skips to the next iteration:

let total = 0
for (i in [1, 2, 3, 4, 5]) {
    if (i == 3) { continue }   // skip 3
    if (i == 5) { break }      // stop before 5
    total += i
}
print(total)   // Output: 3  (1 + 2)

Return Statements

Functions can return values using return. If no return statement is found, the result of the last expression is returned (implicit return), but explicit return is supported for early exit.

let check = fn(x) {
    if (x < 0) {
        return "negative"
    }
    return "positive"
}

Try / Catch

Wrap code that might fail in a try block and handle the failure in catch. The caught error is bound to the name you provide in parentheses:

fn safeDiv(p, q) {
    try {
        return p / q
    } catch (e) {
        return -1
    }
}
 
print(safeDiv(10, 2))   // 5
print(safeDiv(10, 0))   // -1  (division by zero was caught)

try/catch also catches runtime errors such as accessing an undefined variable:

let captured = "none"
try {
    let bad = undefinedThing
} catch (e) {
    captured = "caught"
}
print(captured)   // caught

Portability note: The error value bound in catch carries a human-readable message. The exact text — in particular whether it is prefixed with a source position like line X, col Y: — can vary between SDKs. If you need byte-identical output across every engine, avoid printing the raw error and emit a fixed marker instead (as shown above).