how to add digit of a given number code example

Example 1: adding digits of a number in c

//program to find the sum of digits:

#include<stdio.h>
int main()
{
  int num,sum=0,r,temp;
  printf("Enter the number:\n ");  //taking input from the user
  scanf("%d",&num);
  
  temp=num;           //assigning num to temporary variable
  
  while(temp!=0)
  {
    r=temp%10;
    sum=sum+r;
    temp=temp/10;
  }
  printf("\nGiven number = %d",num);
  printf("\nSum of the digits = %d",sum);
}

//code By dungriyal

Example 2: Write a function digitsum that calculates the digit sum of an integer. The digit sum of an integer is the sum of all its digits.

function digSum(n) {
    let sum = 0;
    let str = n.toString();
    console.log(parseInt(str.substring(0, 1)));
    for (let i = 0; i < str.length; i++) {
        sum += parseInt(str.substring(i,i+1));
        
    }
    return sum;
}