SOURCE

function jc(num) {
    let result = [0, 1, 2]

    function calc(num) {
        if (num < 2) {
            return result[num]
        }
        if (result[num]) {
            return result[num]
        }

        result[num] = num * calc(num - 1)
        console.log(result)
        return result[num]
    }

    return calc(num)
}

console.log(jc(5))