Is it worth caching the length of an array in a Javascript loop? (v179)

Revision 179 of this benchmark created on

Description

http://stackoverflow.com/questions/5349425/whats-the-best-to-loop-an-array-in-javascript

Preparation HTML

<script>
  var myArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20];
  var total = 0,
      len = myArray.length,
      i = 0;
</script>

Test runner

Ready to run.

Testing in
TestOps/sec
With caching
for (var i = 0, len = myArray.length; i < len; i++) {
  total++;
}
ready
Without caching
for (var i = 0; i < myArray.length; i++) {
  total++;
}
ready
Counting down
for (var i = myArray.length; i--;) {
  total++;
}
ready
caching length outside for loop
for (; i < len; i++) {
  total++;
}
ready
caching length outside for counting down loop
for (var i = len; i--;) {
  total++;
}
ready
With caching Pre
for (var i = 0, len = myArray.length; i < len; ++i) {
  total++;
}
ready
TT Loop
for (; i < len; ++i) {
  total++;
}
ready

Revisions

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