Is it worth caching the length of an array in a Javascript loop? (v47)

Revision 47 of this benchmark created by PhiLho 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];
</script>

Test runner

Ready to run.

Testing in
TestOps/sec
With caching
for (var i = 0, len = myArray.length; i < len; i++) {

}
ready
Without caching
for (var i = 0; i < myArray.length; i++) {

}
ready
Counting down
for (var i = myArray.length; i--;) {

}
ready
caching length outside for loop
var len = myArray.length;
for (var i = 0; i < len; i++) {

}
ready
while loop
var len = myArray.length;
while (len--) {

}
ready
for check index
for (var i = 0; myArray[i++];) {

}
// Interesting attempt, but fails if myArray contains 0 or equivalent!
ready
for in
for (var i in myArray) {

}
ready
With caching and pre-increment
for (var i = 0, len = myArray.length; i < len; ++i) {

}
ready

Revisions

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