整数转罗马数字

/**
 * @param {number} num
 * @return {string}
 */
var intToRoman = function(num) {
    //创建自己的字典然后依次减下去
    let nums=[1000,900,500,400,100,90,50,40,10,9,5,4,1],
        chars=['M','CM','D','CD','C','XC','L','XL','X','IX','V','IV','I'];
    let result='';
    while(num){
        if(num>=nums[0]){
            result+=chars[0];
            num-=nums[0];
        }else{
            nums.shift();
            chars.shift();
        }
    }
    return result;
};