随机字符串生成指定范围内的某个数值

 1 function imgNum(id, num) {
 2     let arr = id.split(""),
 3         sum = 0;
 4     arr.forEach(val => sum += val.charCodeAt());
 5     return sum % num
 6 }
 7 imgNum("quroqfehfrk-3-4-5whr", 20);
 8 //6
 9 imgNum("2quroqfehfrk-3-4-5whr", 20);
10 //16
11 imgNum("3quroqfehfrk-3-4-5whr", 20);
12 //17
13 imgNum("9quroqfehfrk-3-4-5whr", 20);