Fastest array loops in Javascript (v424)

Revision 424 of this benchmark created by docvox on

Preparation HTML

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

  var it = 0;
  var bIt = arr.length;

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

Test runner

Ready to run.

Testing in
TestOps/sec
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
Order
while (i = arr.shift()) {
  someFn(i);
}
ready
forEach
arr.forEach(function(v) {
  someFn(v)
})
ready
order validation
while ((i = arr.shift()) !== undefined) {
  someFn(i);
}
ready
While ! Undefined
var a;
while ((a = arr[i++]) !== undefined) {
  someFn(a);
}
ready
Pop
while (i = arr.pop()) {
  someFn(i);
}
ready
Order w/ array copy
var copy = arr.slice(0);
while (i = copy.shift()) {
  someFn(i);
}
ready
While length--
var l = arr.length;
while (l--) {
  someFn(arr[l]);
}
ready
for without final-expression
for (var i = arr.length; --i >= 0;) {
  someFn(arr[i]);
}
ready
While loop, basic With Global I
it = 0;
while (it < arr.length) {
  someFn(arr[it]);
  it++;
}
ready
While length-- 2
var l = arr.length;
while (l) {
  someFn(arr[arr.length - l--]);
}
ready
While length-- 3
var l = arr.length;
var lng = l;
while (l) {
  someFn(arr[lng - l--]);
}
ready
reverse while loop
var l = arr.length;
while (l) {
  someFn(arr[--l]);
}
ready

Revisions

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