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by leptons 595 days ago
We don't make any external HTTP requests for any library code. jQuery is embedded into the page HTML file, along with all other required library code necessary for the page to start functioning, in one bundle. Nothing that runs below the fold is executed until the page is scrolled. All scripts are deferred, except the required libraries, one of which is jQuery and is loaded in-line in a <script> block in the page <head>. There's a ton of tricks we use to get to a perfect Google Lighthouse score - we also score perfect 100% on mobile too. This isn't a complex web application but we do a lot of cool front-end stuff.
1 comments
Rapzid 595 days ago
That's great and fair. Some places are NUTS about first page load speed(and I mean first time someone has ever visited the site) though and it really could matter across all deps depending on a ton of other factors..

Serving super common libs, like jQuery, from the lost likely CDN location could maximize the likelihood it's already cached.

I have never personally worked anywhere this mattered.

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leptons 594 days ago
We provide a website among many other services to our clients. Our clients are very SEO focused, and they will go to Google's Lighthouse (or another testing site) to test their site's page speed, and then they will put in the URL for their competition's website to see how their site compares to their competitors. If they see their page speed score is 1/2 as fast as their competition, they have a reason to leave us and find a better host (whoever their competition is using). We have thousands of clients, so I am managing thousands of individual customized websites based on core "white-label" template code. Page speed matters to us very much, because it matters to our clients.

Google Lighthouse will complain about every HTTP request, and it doesn't care about CDN caching, because none of the external code will be cached when the test is run. It will tell you to minimize external HTTP requests. This is the same way every page speed test works, not just Google. So including any external dependency will cause the page speed score to go down a bit. Have enough of them and your page speed score ends up being very poor (many other factors can affect this, all of which are detailed in the Lighthouse report). It doesn't matter what the average site visitor experiences if their cache has jQuery in it from some random CDN. The only thing that really matters is that Google is telling our client that their site is performing badly compared to their competitor's site.

So, my job is to make sure our clients never, ever think about leaving us because of page load speed as measured by Google or any other testing site. Our clients pay us hundreds of dollars every month, some of them pay 10s of thousands depending on their needs (we don't just provide websites). So there is a lot of money at stake. Page speed scores matter very much to us. When our client sees their site is scoring perfect 100% on all Lighthouse tests, and their competitor is scoring a 70%, then we win, and the client has one less reason to leave. We even use this as a selling point to bring on new clients, because we have an absolutely untouchable page speed score compared to our competitors in this space.

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Rapzid 594 days ago
I'm not sure what to say, I believe you but you seem to be talking past my point that other companies may prefer to go a different route based on their needs and what they are optimizing for. There are real situations a CDN may be preferred.
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leptons 593 days ago
Companies that are using CDNs to load commonly used libraries aren't actually interested in page load speed scores. They're pursuing a tech trick that was always somewhat of a red herring, and frankly a bit risky. We've experimented with CDNs and they have actually added stuff to the libraries that shouldn't be there. Trusting a 3rd party to load library code from isn't great for security.
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Rapzid 593 days ago
Right, I didn't say anything about scores. Just adding another point of view.
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