Is it worth caching the length of an array in a Javascript loop? (v159)

Revision 159 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 = [];
  for (var i = 1000; i; i--) {
    myArray.push(Math.random());
  }
</script>

Test runner

Ready to run.

Testing in
TestOps/sec
With caching
var arr = [];
for (var i = 0, len = myArray.length; i < len; i++) {
  arr.push(i);
}
ready
Without caching
var arr = [];
for (var i = 0; i < myArray.length; i++) {
  arr.push(i);
}
ready
Counting down
var arr = [];
for (var i = myArray.length; i--;) {
  arr.push(i);
}
ready
caching length outside for loop
var arr = [];
var len = myArray.length;

for (var i = 0; i < len; i++) {
  arr.push(i);
}
ready
while loop
var arr = [];
var len = myArray.length;
while (len--) {
  arr.push(len);
}
ready

Revisions

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