Happy Number【202】

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

给定一个正整数n，用n的各个位的平方和迭代n。最终会得到平方和为1或者无限循环。这个过程以1结尾的数字是快乐的数字。
例如：
n = 19；
n = 1^2+9^2 = 82
n = 8^2+2^2 = 68
n = 6^2+8^2 = 100
n = 1^2+0^6+0^2 = 1
则19就是快乐数。
解题思路：
想要判断任意一个正整数是不是happy数，首先要算出这个数的平方和；

function digitSquareSum(n){    var sum = 0, m = 0;    while(n!=0){        m = n % 10;        sum += m*m        n = parseInt(n/10);    }    return sum;}

再判断这个数的平方和是不是为1，等于1则是happy数；不是则继续执行计算平方和这一过程，但是首先要判断这个数的平方和是不是在循环，即之前出现过。

var isHappy = function(n){    if(n==1){ return true; }    var obj = {};    while(n != 1){        n = digitSquareSum(n);        if(n==1){            return true;        }else if(obj.hasOwnProperty(n)){            return false;        }else{            obj[n] = true;        }    }}