CodeFights - JavaScript code to calculate the sum of all digits in an integer

digitSum.js

function digitSum(n) {
	var sum = 0;
	var string = n.toString();

	for(i=0; i < string.length; i++){
		sum = sum + parseInt(string.substring(i, i+1));
	}

	return sum;
}

You can also just return n%9. I know its not as interesting. But its faster and smaller.

You can also just return n%9. I know its not as interesting. But its faster and smaller.

sorry but, if your n = 28, the output will be 1 ( 28%9 = 1 ) instead of 10

You are right. Sorry about that. The n%9 is only if you want to keep adding the digits until you have only one digit left.