递归的方式重写阶乘的函数，寻找喇叭花数的循环时报错

我用递归的方式重写阶乘的函数，再套用寻找喇叭花数的循环，浏览器就会报错，请问是什么原因？

// function factorial(num) {

//     let result = 1;

//     for (let i = num; i > 1; i--) {

//         result *= i;

//     }

//     return result;

// }

function factorial(num) {

if (num == 1) return 1;

return num * factorial(num - 1);

}

for (let i = 100; i <= 999; i++) {

let a = parseInt(i / 100);

let b = parseInt(i / 10) % 10;

let c = i % 10;

if (i == factorial(a) + factorial(b) + factorial(c)) console.log(i);

}

chrome 报错如下：

test.html:22 Uncaught RangeError: Maximum call stack size exceeded

    at factorial (test.html:22:13)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

    at factorial (test.html:23:26)

指向的是  if (num == 1) return 1; 这行代码。