Loops (long array) (more accurate tests)

JavaScript performance comparison

Revision 10 of this test case created by Thomas Aylott

Info

Creates the array with actual values and uses the result in an expression to keep the browser from optimizing in weird ways or something maybe.

Preparation code

<script>
  var arr = [1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3];
 
  var something = 0
</script>

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

Java applet disabled.

Testing in unknown unknown
Test Ops/sec
while loop that imitates a for loop
var i = 0;
while (i < arr.length) {
 something + arr[i];
 i++;
};
pending…
while loop that imitates a for loop, caching the length
var i = 0,
    len = arr.length;
while (i < len) {
 something + arr[i];
 i++;
};
pending…
Reverse while loop
var i = arr.length;
while (i--) {
 something + arr[i];
};
pending…
Reverse do … while loop
var i = arr.length;
do {
 something + arr[i];
} while (i--);
pending…
Reverse for loop
for (var i = arr.length; i--;) {
 something + arr[i];
};
pending…
Old ’n’ busted for loop
for (var i = 0; i < arr.length; ++i) {
 something + arr[i];
};
pending…
Old ’n’ busted for loop, caching the length
for (var i = 0, len = arr.length; i < len; ++i) {
 something + arr[i];
};
pending…
Cool guy loop
for (var i = -1; ++i < arr.length;) {
 something + arr[i];
};
pending…
Cool guy loop, caching the length
for (var i = -1, len = arr.length; ++i < len;) {
 something + arr[i];
};
pending…
Native Array#forEach implementation
arr.forEach(function(x) {
 something + x;
});
pending…
Native Array#forEach implementation with named function
function foo(x) {
 something + x;
};
arr.forEach(foo);
pending…
Unrolled loop
for (var i = 0, len = arr.length; i < len; i = i + 10) {
 something + arr[i];
 something + arr[i + 1];
 something + arr[i + 2];
 something + arr[i + 3];
 something + arr[i + 4];
 something + arr[i + 5];
 something + arr[i + 6];
 something + arr[i + 7];
 something + arr[i + 8];
 something + arr[i + 9];
};
pending…
Native Array#forEach with cached function
// This one is faster because it only creates the function on its first run
// So the more iterations it runs, the faster it'll be relative to the other tests
if (!window.forEachMe) window.forEachMe = function(x) {
 something + x
}

arr.forEach(forEachMe);
pending…

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Revisions

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