for of vs for

common.html

<script>
  var array = [];
  for (var i = 0; i < 1000; i++) {
    array[i] = i;
  }
</script>

for.js

var sum = 0;
for (var i = 0, len = array.length; i < len; i++) {
  sum += array[i];
}

forof.js

var sum = 0;
for (var x of array) {
  sum += x;
}