Is it worth caching the length of an array in a Javascript loop? (v146)

Revision 146 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 fib  = function(n){
      if(n<2){
         return 1;
      }
      return fib(n-1)+fib(n-2);
  }
  var fib20 = fib.bind(null,20);
</script>

Test runner

Ready to run.

Testing in
TestOps/sec
With caching
for (var i = 0, len = myArray.length; i < len; i++) {
    fib20();
}
ready
Without caching
for (var i = 0; i < myArray.length; i++) {
    fib20();
}
ready
Counting down
for (var i = myArray.length; i--;) {
    fib20();
}
ready
caching length outside for loop
len = myArray.length;

for (var i = 0; i < len; i++) {
    fib20();
}
ready
while loop
len = myArray.length;
while (len--) {
     fib20();
}
ready
for check index
for (var i = 0; myArray[i++];) {
    fib20();
}
ready

Revisions

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