var arr = [];
var count = 100000;
for(var i = 0; i<count; i++)
{
arr.push(i);
}
var arrLen = arr.length;
var sum = 0;
for (var i = 0; i < arrLen; i++){
sum = arr[i];
}
var sum = 0;
for (var i in arr){
sum = arr[i];
}
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
Cache length | |
Do not cache |
Test name | Executions per second |
---|---|
Cache length | 126.9 Ops/sec |
Do not cache | 120.0 Ops/sec |
Let's dive into the world of MeasureThat.net and analyze the provided benchmark.
Benchmark Overview
The provided benchmark measures the performance difference between two approaches to saving the length of an array in a variable versus retrieving it within a loop. The test cases compare caching the array length or not caching it.
Options Compared
Two options are compared:
var arrLen = arr.length
) and uses it as the condition for the loop.in
operator to check if each element is an index of the array.Pros and Cons
arrLen
might be higher than not using it at all. Additionally, this approach assumes that the array will have the same length for each iteration, which might not be the case in practice.in
. This can lead to slower performance.Library and Special Features
There are no external libraries used in this benchmark. However, the use of the in
operator (for (var i in arr)
) is specific to JavaScript and allows iterating over the properties of an object (including arrays).
Other Considerations
When dealing with arrays in JavaScript, it's essential to consider the following:
arr[i]
can be faster than using arr[index]
since indexing is optimized for arrays.in
operator can lead to slower performance due to the overhead of iterating over the array's properties.Alternatives
Other alternatives to compare in a benchmark could include:
length
property directly: Instead of assigning it to a variable, use arr.length
directly in the loop condition.for...of
loop: Consider using a for...of
loop instead of a traditional for
loop for iterating over arrays. The former is more concise and expressive.These alternatives might provide different insights into the performance characteristics of each approach, depending on the specific use case and browser/interpreter used.