How to fold the values of the elements of two arrays in js?

// Sum all elements
sumOfAllElements function(arr1, arr2) {
 sumOfArr1 = arr1.reduce((sum, el) => sum + el, 0);
 sumOfArr2 = arr2.reduce((sum, el) => sum + el, 0);

 return sumOfArr1 + sumOfArr2;
}

// Sum of vectors provided that their length is equal
sumOfVectors function(vec1, vec2) {
 var i = 0, result = [];

 while(i < vec1.length/2) {
 result[i] = vec1[i] + vec2[i];
 var j = vec1.length - 1 - i;
 result[j] = vec1[j] + vec2[j];

i++;
}

 return result;
}