sum range javascript

1ar sum = 0;
2  for (var i = Math.min(...arr); i <= Math.max(...arr); i++) {
3    sum += i;
4  }

1function sumAll(arr) {
2    let fullArr = [];
3    let sum = 0;
4    const reducer = (accumulator, currentValue) => accumulator + currentValue;
5    arr.sort(function(a, b) {
6        return a - b
7    });
8    for (let i = arr[0]; i <= arr[1]; i++) {
9        fullArr.push(i);
10    }
11    sum = fullArr.reduce(reducer);
12    return sum;
13}