Performance Newsletter OPEN SOURCE # Loading CSS asynchronously with preload

Remember the newly released specification allowing us to prioritize and prefetch critical assets? (If not, definitely check out [The Critical Request](https://css-tricks.com/the-critical-request/), offering a deep dive into this subject)

[Scott Jehl](https://twitter.com/scottjehl) wrote about using preload to asynchronously serve critical CSS. Knowing about the sparse support, folks at [Filament Group](https://www.filamentgroup.com/) also released a polyfill enabling **link rel=****"preload****"** for browsers without this functionality. Yay! ✨

[Modern Asynchronous CSS Loading](https://www.filamentgroup.com/lab/async-css.html)

PRESENTATION # Serving web fonts responsibly with font-display

[Monica Dinculescu](https://twitter.com/notwaldorf?lang=en) gave an excellent talk on web font performance at SmashingConf Barcelona. In her demo, she thoroughly explains the lifetime of a web font as well as the intricacies of **font-display**. 

Check it out to learn how to serve web fonts responsibly, with slower connections in mind 👏🏻

[Fontastic Web Performance](https://font-display.glitch.me/)

RESOURCES # Painting, compositing and getting rid of jank

You might know [Lin Clark](https://twitter.com/linclark) for her fantastic series explaining coding concepts, [Code Cartoons](https://code-cartoons.com/). In her thorough and informative article, Lin describes why rendering at 60fps is important, sheds light on the process of painting and compositing, GPU acceleration and more.

If you want to learn why browsers get janky, have a read. 👩🏻‍🎓

[The whole web at maximum FPS: How WebRender gets rid of jank](https://hacks.mozilla.org/2017/10/the-whole-web-at-maximum-fps-how-webrender-gets-rid-of-jank/)

RESOURCES # Getting your async functions right In his short, but sweet article, [Jake Archibald](https://twitter.com/jaffathecake) explains the subtleties of writing asynchronous functions in JavaScript. If you ever wondered what’s the difference between **await**, **return** and **await return**, look no more. 🕵🏻‍♀️

[Await vs Return vs Return await](https://jakearchibald.com/2017/await-vs-return-vs-return-await/)

RESOURCES # Understanding why performance efforts fail

While [Kat Busch](https://twitter.com/kat_busch) often refers to hardware performance rather than the Web, her thoughts on approaching performance bottlenecks are very relevant no matter the platform. How do we fix bugs without increasing the complexity of a codebase? How do we focus on the right thing?

🤔

[The Rules of Optimization: Why So Many Performance Efforts Fail](https://hackernoon.com/the-rules-of-optimization-why-so-many-performance-efforts-fail-cf06aad89099)

RESOURCES # How fast is JavaScript?

JavaScript popularity is proliferating and the favourite scripting language many times has been dubbed as the fastest out there. Is it though? You will never know what happens next! 😂

🙇🏻‍♀️ To [Franziska Hinkelmann](https://twitter.com/fhinkel), an engineer working on the V8 engine, for thoughtful benchmarks.

[Speed up Your Node.js App with Native Addons](https://medium.com/the-node-js-collection/speed-up-your-node-js-app-with-native-addons-5e76a06f4a40)

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