Finds single digit sum of a number.

singleDigitSumCalculator.js

singleDigitSum = function( number){
  if(number % 9 === 0){
      return 9;
  }
  else{
      return number % 9;
  }
};

do{
    
var number = prompt("Enter number to find single digit sum.Enter 'q' to quit.");
if(number.length > 0 && isNaN(number)===false)
    alert("Single digit sum of " + number + " is: "+ singleDigitSum(number));
else if(number!== 'q')
    alert("Please enter a numeric value.");
} while(number !== 'q');