Program in Javascript to find the sum of N Natural Numbers - using mathematical formula

The below function will help us to find the sum of N Natural numbers using mathematical formula (N*(N+1))/2

function SumofNNaturalNumbers() {

                var N=10;
                var sum = 0;                    
                sum = (N * (N+1)) /2;                                           
                alert("Sum Of N Natural Numbers : " + sum);
            }

We know that the formula for the sum of N Natural numbers is (N*(N+1))/2 . Put the value of N at runtime to get the result.Finally, printing the same using the alert.