Sum Strings as Numbers

function sumStrings(a,b) { 
  if (a.length < b.length) { // make sure a is the longer
    var tmp = a;
    a = b;
    b = tmp;
  }
  
  a = a.split("").reverse()
  b = b.split("").reverse()
  
  var carry = 0;
  var ans = []
  
  for (var i in a) {
    if (i < b.length) {
      var sumT = parseInt(a[i]) + parseInt(b[i]) + carry;
      var sum = sumT % 10;
      carry = (sumT - sum)/10;
      ans.push(sum)
      
    } else {
      ans.push(carry + parseInt(a[i]));
      carry = 0;
    }

  }
  if (carry != 0) {
    ans.push(carry);
  }
  return ans.reverse().join("").replace(/^0/,"")
}