Node can go 3x faster

[Skitionek]

It might sound a bit like sorcery but if you will traverse array backwards you can achieve up to 3 times better performance. The only difference is to use this construction:

for ( var i = array.length; i--; ) {
   (...)
}

There has been prolonged discussion about it on GitHub: https://stackoverflow.com/questions/5349425/whats-the-fastest-way-to-loop-through-an-array-in-javascript
and here you can find related test:
http://jsbench.github.io/#67b13d4e78cdd0d7a7346410d5becf12

I didn't check it in node though but in browser... :
https://jsbench.me/j0jw6pygqu/1

Also as you can see in tests you can gain performance on declaring the data type for array.

Wonder how much improvements can be gain in PHP and if running on node will make the difference.

[gitKearney]

@Skitionek what do you mean traverse array backwards? The test is to sort an array of numbers to be in increasing numerical order.

The sorting algorithm is bubble sort

[thomfoolery]

In order to sort the array you must traverse it

[gitKearney]

🤔
My test results seems to disagree

master  2019-05-27 16:23:29 $ node bubble-sort-v2.js 
[V8] array contains 4001 elements, execution time (reverse): 191.142963 ms
master  2019-05-27 16:23:41 $ node bubble-sort-v2.js 
[V8] array contains 4001 elements, execution time (reverse): 178.461635 ms
master  2019-05-27 16:23:49 $ node bubble-sort-v2.js 
[V8] array contains 4001 elements, execution time (reverse): 178.21798 ms
master  2019-05-27 16:23:51 $ node bubble-sort-v2.js 
[V8] array contains 4001 elements, execution time: 41.697885 ms
master  2019-05-27 16:24:12 $ node bubble-sort-v2.js 
[V8] array contains 4001 elements, execution time: 41.850747 ms
master  2019-05-27 16:24:14 $ node bubble-sort-v2.js 
[V8] array contains 4001 elements, execution time: 40.6025 ms

const reverseBubbleSort = (a) => {
    const len = a.length;

    let sorted = false;
    while(!sorted) {
        sorted = true;
        for (let i = a.length; i >= 0; i--) {
            let current = a[i];
            let next    = a[i - 1];

            if(next > current) {
                a[i] = next;
                a[i - 1] = current;
                sorted = false;
            }
        }
    }
};

Did I do something wrong?

[gitKearney]

In order to sort the array you must traverse it

yes, I know, you must traverse an array to sort it :/

My initial thought was he meant traverse the array backwards and put it into a new array (since the elements are in order of greatest to least) thus eliminating the need for a comparison.

If he had meant change the algorithm, and specified how to update the if conditional test, then I would've understood what he meant more clearly. But, instead he only updated the for loop, leaving the conditional inside a mystery as to how to incrementing the index gets you to the beginning of the array.

[Skitionek]

The difference is not so huge as in a browser yet it is significant. Am I missing something?