Fastest array loops in Javascript (v312)

Revision 312 of this benchmark created on

Preparation HTML

<script>
  function someFn(ix) {
    return ix * 5 + 1 / 3 * 8;
  }
</script>

Setup

// Populate the base array
    var arr = [];
    for (var i = 0; i < 1000; i++) {
      arr[i] = i;
    }

Test runner

Ready to run.

Testing in
TestOps/sec
For loop, basic, cached, reverse
var i = arr.length - 1;
for (; i > -1; i--) {
  someFn(arr[i]);
}
ready
While loop, basic, cached, reverse
var i = arr.length - 1;
while (i) {
  someFn(arr[i]);
  i--;
}
ready
For loop, basic
for (var i = 0; i < arr.length; i++) {
  someFn(arr[i]);
}
ready
While loop, basic
var i = 0;
while (i < arr.length) {
  someFn(arr[i]);
  i++;
}
ready
For loop, cached
for (var i = 0, len = arr.length; i < len; i++) {
  someFn(arr[i]);
}
ready
For loop, i--
for (var i = arr.length; i > 0; i--) {
  someFn(arr[i]);
}
ready
Do-while loop, i--
var i = arr.length - 1;
do {
  someFn(arr[i]);
} while (i--);
ready
Do-while loop, --i
var i = arr.length;
if (i > 0) {
  do {
    someFn(arr[i]);
  } while (--i);
}
ready
For..in loop
for (var i in arr) {
  someFn(arr[i]);
}
ready
While ! Undefined
var a, i = 0;
while ((a = arr[i++]) !== undefined) {
  someFn(a);
}
ready
While length--
var l = arr.length;
while (l--) {
  someFn(arr[l]);
}
ready
Without braces
for (var i = arr.length; --i >= 0; someFn(arr[i]));
ready
For loop, basic, cached
var i = 0,
  len = arr.length;
for (i = 0; i < len; i++) {
  someFn(arr[i]);
}
ready
While loop, basic, cached
var i = 0,
  len = arr.length;
while (i < len) {
  someFn(arr[i]);
  i++;
}
ready

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.