Sum of Digits / Digital Root

[hellocan]

In this kata, you must create a digital root function.
A digital root is the recursive sum of all the digits in a number. Given n, take the sum of the digits of n. If that value has two digits, continue reducing in this way until a single-digit number is produced. This is only applicable to the natural numbers.

Here's how it works (Ruby example given):
digital_root(942)
=> 9 + 4 + 2
=> 15 ...
=> 1 + 5
=> 6

digital_root(132189)
=> 1 + 3 + 2 + 1 + 8 + 9
=> 24 ...
=> 2 + 4
=> 6

digital_root(493193)
=> 4 + 9 + 3 + 1 + 9 + 3
=> 29 ...
=> 2 + 9
=> 11 ...
=> 1 + 1
=> 2

Your Test Cases:
Test.assertEquals( digital_root(16), 7 )

where By
http://www.codewars.com/kata/541c8630095125aba6000c00/train/javascript

[Go7hic]

function digital_root(n) {
   return String(n).split('').map(Number).reduce((i,j) => i+j)
}

[Go7hic]

不知道为啥这个答案过不了

[Go7hic]

哎呀，被你给的信息给误导了。看了原网站的题目才发现，是这个意思：

942
=> 9+4+2
=>15
=>1+5
=>6

是这个意思

[Go7hic]

来个递归就好了

function digital_root(n) {
    var fn = function() {
      return String(n).split('').map(Number).reduce((i,j) => i+j)
    }
   return  fn() > 9 ? digital_root(fn()) : fn()
}

[hellocan]

function digital_root(n) {
    var root = function(){ 
     return String(n).split('').map(Number).reduce((x,y) => x+y)
 }
    return  n <= 9 ? root(n) :  digital_root(root())
}

[hellocan]

哈哈，我粗心了。好像代码格式还是没有你的好看

[Go7hic]

这个题目排名最高的答案给我的感觉就是——程序的数学之美。

[Luffyying]

这个题目排名最高的答案给我的感觉就是——程序的数学之美。

能否解惑下这个答案呢，😂

[ool3]

хехе