codewars--js--Roman Numerals Encode

问题描述：（将阿拉伯数字转换成罗马数字）

Create a function taking a positive integer as its parameter and returning a string containing the Roman Numeral representation of that integer.

Modern Roman numerals are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero. In Roman numerals 1990 is rendered: 1000=M, 900=CM, 90=XC; resulting in MCMXC. 2008 is written as 2000=MM, 8=VIII; or MMVIII. 1666 uses each Roman symbol in descending order: MDCLXVI.

Example:

solution(1000); // should return 'M'

Help:

Symbol    Value
I          1
V          5
X          10
L          50
C          100
D          500
M          1,000

Remember that there can't be more than 3 identical symbols in a row.

优秀答案：

 function solution(number){
   // convert the number to a roman numeral
 var  roman = {M:1000,CM:900, D:500,CD:400,C:100,XC:90,L:50,XL:40,X:10,IX:9,V:5,IV:4,I:1 }

 var ans = '';
 while(number>0){
     for(a in roman){
         if(roman[a]<=number){ ans += a; number-=roman[a]; break;}

     }
 }
 return ans;
 }