[LeetCode][JavaScript]Ugly Number

Ugly Number 

Write a program to check whether a given number is an ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.

https://leetcode.com/problems/ugly-number/

---

质因数只能包含2,3和5。

直接去除2,3和5，除到剩1为止。

/**
 * @param {number} num
 * @return {boolean}
 */
var isUgly = function(num) {
    if(num <= 0){
        return false;
    }
    while(num !== 1){
        if(num % 2 === 0){
            num /= 2;
            continue;
        }
        if(num % 3 === 0){
            num /= 3;
            continue;
        }
        if(num % 5 === 0){
            num /= 5;
            continue;
        }
        return false;
    }
    return true;
};