Sum all numbers in a range - numbers concatenating instead of adding up

JavaScript
1

why are my numbers concatenation and not adding up?

function sumAll(arr) {
  var ans = arr.reduce(function(a, b){
    var min = Math.min(a, b);
    var max = Math.max(a, b);
    var result = "";
    for(  min = min;min <= max; min++){
      result += min;
    }
    return result;
  });
  return ans;
}

sumAll([1, 4]);
3

Wow Thank You, that was easy. it was my first time building up the courage to post, I really appreciated it.