The js solution to sum of all numbers from 1 to n

sumOfAllNum.js

//my solution
function f(n){
  return n > 0 && n % 1 === 0 ? ((1+n)*n)/2 : false;
};

//good examples
//1
function f(n){
  return (parseInt(n) === n && n > 0) ? n*(n+1)/2 : false;
};
//2
function f(n){
  return n > 0 && !(n % 1) ? n * ++n / 2 : false;
}