I came across a rather peculiar implementation of a string repeat function for JavaScript.

There's a built-in for this since ES2015, and prior to that, the following was a common idom:

> str = "x"
> count = 3
> out = (new Array(count + 1).join(str)

But, an MDN contributor thought - we can optimize this! Can you figure out how and why it works?

👉 codepen.io/Krinkle/pen/abmrLdz

"Why we are not adding AVIF support (yet)" by Dejan Pelzel.

The founder of BunnyCDN shares their technical analysis and what needs improving first.

- Terrible server encoding perf, unsuitable for on-demand, even with disproportionate resources. (Better algos?)
- Slow to decode/render. (Better algo, hardware support?)
- No progressive render, not even basic linear. (All or nothing.)

Bandwidth isn't everything :)


"Electron alternatives?" by Dimitri Witkowski

The author of KeeWeb offers a fresh and nuanced perspective. Personally, I find download/update size reason enough to switch to Ultralight-UX, , or Tauri, etc.

But, popular opinion against Electron is driven by RAM use and slowness, which evidently aren't caused by but by poor engineering atop of it...

KeeWeb is fast and uses 150-200M, with or without Electron.


"Easy to design, hard to use"

A conversation with Chris Coyier and Gerry McGovern:

> If web developers made cars, you'd put the pedal to the metal on them and go at 40 miles an hour, maximum speed. We think we're designing Ferraris, but we're designing tractors.


"Emergency" by Chris Taylor.

A geeky fan fiction on web performance. Featuring, among others: Dr Lea Verou, Jen Simmons, and Dr Lawson - the HTML love-doctor.

Listen up people, we have a patient in a serious condition here. 12 year old e-commerce website, recently undergone a redesign – and [...]


"The Website Obesity Crisis" by Maciej Cegłowski

Approachable and funny talk on the state of performance, UX design, and overpriced clouds.

I was humbled by the fresh and optimistic approach to it all. I've fought this crisis for a long time, but never seen it laid out so well and so clearly. Great refresher if nothing else!

> "Complexity is a bug lamp for smart people."

H/T @pbanks


"Profiling live Wikipedia traffic with near-zero overhead"

> Each day of Wikipedia backend traffic yields about 3 million stack trace samples, as collected by Excimer, a new a low-overhead sampling profiler for PHP.

I wrote all about it in this year's Performance Calendar:

👉 calendar.perfplanet.com/2020/p

"How life works in Antarctica" by Wendover

Mini-docu on how it is to live (and work) at our South Pole. Some takeaways:

- Network speeds are limited to 38 kbit/s (!) most of the day. Almost on par with 90s telephone dial-up.
- Rescue operations are harder than for the ISS in outer space. They're cut off 9 months a year.
- It remains the only covid-free continent.

Nebula: watchnebula.com/videos/wendove
YT: youtu.be/ZAEydOjNWyQ

"Europe vs USA Broadband Performance (2020 Report)"

From FairInternetReport:
> American internet users have had a very good 2020: […] median Internet speeds doubled [from] 17.34mbps in 2019 to 33.16mbps in 2020 […] increased 91%.
> US average broadband speeds overtook western EU countries […] for the first time in 5 years.
> The US stills lags behind many European and developed nations […]
> Italy continues to have the worst internet in the EU, […]


"Impact of using HTTP connection pooling for PHP applications at scale", by Giuseppe Lavagetto (Wikimedia)

- using Envoy,
- backend service's CPU usage went from 2.5 CPU cores to circa 0.8 CPU cores,
- PHP application's latency histogram bucket for <= 100ms went up by 12 percentage points.


"Cumulative Layout Shift, in practice" by Nic Jansma.

Great overview of this new web performance API.


This independent comparison finds WebP has a fairly narrow sweet spot for a certain type and dimension of photos where it is ~9% smaller than JPEG.

For other types and sizes it is on-par.. or larger?


Interesting correlations (and lack thereof) between "Save Data" preferences and various national socio-economic statistics, income distribution, cost of bandwidth, device, and connectivity type.

Also, data is really cheap in India! … and in most of Europe; whilst insanely expensive in the US, topped only by Canada and the Cayman Islands.


Videos from the Web Performance track by Wikipedia at FOSDOM are up at:


The conference took place Feb 1st in Brussels.

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