Optimise SOX

[shu8]

SOX can sometimes add up to a few seconds to page load times, and its performance seems to decrease as more features are enabled.

This causes users to have to think about which features they want most rather than enabling all that they like.

Whilst SOX inevitably will cause some increase in load times due to the changes/insertions it does to the DOM, I'm confident it can be improved.

I logged some very quick timing data on the time it takes from the first feature to load till the last using the features I have enabled (I have 50 out of the current 79 available enabled):

• 216.962890625ms
• 317.482177734375ms
• 404.2578125ms
• 197.465087890625ms
• 527.699951171875ms

They seem to range from 200ms to 500ms. I'm not entirely sure how they're so different but it would be great to reduce this!

Some ideas on what I'm planning to do at first:

• [x] Go through SOX's use of jQuery and try to optimise inefficient selectors/replace them with vanilla JS. jQuery's docs and this tutorial mention some ways jQuery selectors can be improved
• [x] Cache DOM elements that have already been queried
• [x] Look into how efficient the Mutation Observers are now Many SOX features rely on Mutation Observers so they can react to changes in the DOM. This has led to SOX adding lots of different ones for different areas of the page, and I'm sure some of them could at least be made more specific. Alternatively have a single Mutation Observer for SOX which each feature hooks into to find changes it's interested in. Performance of MutationObserver to detect nodes in entire DOM is an interesting read
• [x] See if the Chrome Dev Tools Profiler can be of any use in optimising SOX
• [x] Start maintaining some sort of cache of API request results -- a very common browse on SE sites must definitely result in lots of very similar/same API requests (e.g. getting a user's details, or a post's revisions). Caching for even a minute or two might reduce the number of requests made

If anyone has any other ideas, please do comment here, or submit a pull request!

[shu8]

With these changes, I've seen times go down to ones along these lines:

• 126.412109375ms
• 133.839111328125ms
• 150.77001953125ms
• 164.4970703125ms

I'm fairly sure I'm using the same SE page I used to get the original numbers in this issue, and it definitely does seem to have improved.

Whilst there may (will!) be more improvements to be made, I've finished the main things I wanted to do (cache API responses, improve MutationObservers), so I'm going to close this and release v2.5.0 to master.