Negative number digit sum in JavaScript

We are required to write a JavaScript function that takes in a negative integer and returns the sum of its digits.

For example: If the number is −

-5456

Output

Then the output should be −

5+4+5+6
10

Example

The code for this will be −

const num = -5456;
const sumNum = num => {
   return String(num).split("").reduce((acc, val, ind) => {
      if(ind === 0){
         return acc;
      }
      if(ind === 1){
         acc -= +val;
         return acc;
      };
      acc += +val;
      return acc;
   }, 0);
};
console.log(sumNum(num));

Output

The output in the console −

10