Using type guard

Com verificar se o tipo especifico quando são tipos primitivos podemos usar a keyword typeof que retorna o tipo pertencente a aquele valor

function calculateTax(amount: number, format: boolean): string | number {
    const calcAmount = amount * 1.2;
    return format ? `$${calcAmount.toFixed(2)}` : calcAmount;
}

let taxValue = calculateTax(100, false);

if (typeof taxValue === "number") {
    console.log(`Number Value: ${taxValue.toFixed(2)}`);
} else if (typeof taxValue === "string") {
    console.log(`String Value: ${taxValue.charAt(0)}`);
}

Usando o Type Guard com switch

function calculateTax(amount: number, format: boolean): string | number {
    const calcAmount = amount * 1.2;
    return format ? `$${calcAmount.toFixed(2)}` : calcAmount;
}

let taxValue = calculateTax(100, false);

switch (typeof taxValue) {
    case "number":
        console.log(`Number Value: ${taxValue.toFixed(2)}`);
        break;
    case "string":
        console.log(`String Value: ${taxValue.charAt(0)}`);
        break;
}

11 November 2025