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

JavaScript performance comparison

Revision 117 of this test case created by Ernest

Info

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

Preparation code

<script>
  var myArray = new Array(100);
</script>

Test runner

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

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

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

}
 pending…
caching length outside for loop
 
var len = myArray.length;

for (var i = 0; i < len; i++) {

}
 pending…
while loop
 
var len = myArray.length;
while (len--) {
 // blah blah
}
 pending…
Caching and incrementing inside for loop
 
for (var i = 0, len = myArray.length; i < len; ) {
  i++;
}
 pending…
while loop counting up
 
var len = myArray.length;
var i = 0;
while (i < len) {
  i++;
}
 pending…
while loop counting up with !==
 
var len = myArray.length;
var i = 0;
while (i !== len) {
  i++;
}
 pending…

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