Is it worth caching the length of an array in a Javascript loop? (v189)

Revision 189 of this benchmark created by Val Baca on

Description

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

Preparation HTML

<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>
<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, b = 0; i < len; i++) {
  b = myArray[i]
}
ready
Without caching
for (var i = 0, b = 0; i < myArray.length; i++) {
  b = myArray[i]
}
ready
Counting down
for (var i = myArray.length, b = 0; i--;) {
  b = myArray[i]
}
ready
caching length outside for loop
len = myArray.length, b = 0;

for (var i = 0; i < len; i++) {
  b = myArray[i]
}
ready
while loop
var a = myArray.length,
    b = 0;
while (a--) {
  b = myArray[a]
}
ready
for check index
for (var i = 0, b = 0, c; c = myArray[i++];) {
  b = c
}
ready
for in
var b = 0;
for (i in myArray) {
  b = myArray[i]
}
ready
jQuery loop
var b = 0;
$.each(myArray, function(i) {
  b = myArray[i]
});
ready
Using not-equals (with caching)
for (var i = 0, len = myArray.length, b = 0; i !== len; i++) {
  b = myArray[i]
}
ready
Using prefix ++ (using caching)
for (var i = 0, len = myArray.length, b = 0; i < len; ++i) {
  b = myArray[i]
}
ready

Revisions

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