js实现n阶乘

function factorialRecursive(n) {
    if (n === 0 || n === 1) {
        return 1;
    }
    return n * factorialRecursive(n - 1);
}

// 使用示例
console.log(factorialRecursive(5)); // 输出: 120

function factorialIterative(n) {
    let result = 1;
    for (let i = 2; i <= n; i++) {
        result *= i;
    }
    return result;
}

// 使用示例
console.log(factorialIterative(5)); // 输出: 120

function factorialBigInt(n) {
    let result = BigInt(1);
    for (let i = 2; i <= n; i++) {
        result *= BigInt(i);
    }
    return result;
}

// 使用示例
console.log(factorialBigInt(20).toString()); // 输出: 2432902008176640000