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Checking performance of Array.reverse() vs custom loops.
Also see http://jsperf.com/forloop-vs-reverse-while-loop-and-array-reverse/9.
Edited to make sure JIT isn't being "smart" and doing some extra optimizations that won't exist on real applications, also increased the number of items to 1000 to represent a common scenario (perf usually changes drastically based on amount of items, some techniques might only be fast for a short amount of items). See: http://blog.millermedeiros.com/benchmarking-is-hard/
// at least 1K items to make sure it's fast, performnace usually changes
// based on the amount of items
var array = [];
var n = 1000;
while (n--) {
array.push(n * Math.random());
}
// we store result outside of test scope to make sure JIT isn't simply ignoring
// the operations on some cases
var result;
// implementations
// ---------------
// note that the behavior isn't the same on all methods, some are "destructive"
// while others returns a new Array. It's like comparing apples to oranges.
function arrReverse(array){
return array.reverse();
}
function pushSlice(array){
var left = 0;
var length = array.length;
while (left < length) {
array.push(array[length - 1 - ++left]);
array.splice(length - 1 - left, 1);
}
return array;
}
function whileForward(array){
var left = 0;
var length = array.length;
while (left < length) {
var right = length - 1 - left;
array.push(array[right]);
array.splice(right, 1);
left += 1;
}
return array;
}
function forThenSlice(array){
var length = array.length;
for (length -= 2; length > -1; length -= 1) {
array.push(array[length]);
array.splice(length, 1);
}
return array;
}
function forPush(array){
var length = array.length;
var result = [];
var i = null;
for (i = length - 1; i >= 0; i -= 1) {
result.push(array[i]);
}
return result;
}
function forSwap(array){
var length = array.length;
var left = null;
var right = null;
for (left = 0, right = length - 1; left < right; left += 1, right -= 1) {
var temporary = array[left];
array[left] = array[right];
array[right] = temporary;
}
return array;
}
function forSwapHalf(array){
var length = array.length;
var left = null;
var right = null;
for (left = 0; left < length / 2; left += 1) {
right = length - 1 - left;
var temporary = array[left];
array[left] = array[right];
array[right] = temporary;
}
return array;
}
function xorSwap(array){
var length = array.length;
var i = null;
var r = null;
for (i = 0, r = length - 1; i < r; i += 1, r -= 1) {
var left = array[i];
var right = array[r];
left ^= right;
right ^= left;
left ^= right;
array[i] = left;
array[r] = right;
}
return array;
}
function xorSwapHalf(array){
var length = array.length;
var i = null;
var r = null;
for (i = 0; i < length / 2; i += 1) {
r = length - 1 - i;
var left = array[i];
var right = array[r];
left ^= right;
right ^= left;
left ^= right;
array[i] = left;
array[r] = right;
}
return array;
}
function forSwapHalfNonDestructive(arr) {
var results = [];
for (var i = 0, j = arr.length, k; i < j / 2; i += 1) {
k = j - 1 - i;
results[i] = arr[k];
results[k] = arr[i];
}
return results;
}
Ready to run.
Test | Ops/sec | |
---|---|---|
Array.reverse() |
| ready |
while push then slice |
| ready |
while forward |
| ready |
for push then slice |
| ready |
for push |
| ready |
for swap |
| ready |
for swap half |
| ready |
XOR swap |
| ready |
XOR swap half |
| ready |
for swap half non-destructive |
| ready |
You can edit these tests or add more tests to this page by appending /edit to the URL.