AiA 267: JavaScript Performance with Tammy Everts

00:00 12:28
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In this episode of Adventures in Angular Charles Max Wood joins Tammy Everts at JAMstack Confer. Tammy gives a listeners a sneak peek into her talk about website performance, more specifically JavaScript performance. Charles discusses the performance of and Google Lighthouse scores. Tammy explains that while Google Lighthouse is good it isn’t completely reliable and can miss chunks of time when your JavaScript is failing and you have unhappy users.

Tammy shares ways to drill down and see how your JavaScript is behaving in the wild. She talks about blocking Javascript which every developer is familiar with and non-blocking JavaScript that has high blocking CPU time which makes for janky sites. Tammy and Charles discuss what CPU is and what it measures. Tammy names resources and tools to help avoid this problem.

Rules of thumb for avoiding these issues are explained by Tammy. First, Reduce, make sure all the JavaScript needs to be there. Next, Monitor, track your metrics. She also suggests working with vendors and maintaining a performance budget for metrics that matter. The interview ends with a little about Speedcurve and what they do. Tammy is the CXO of Speedcurve.


  • Charles Wood


  • Tammy Everts

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What makes Google Lighthouse scores less reliable?

It only captures a synthetic snapshot and misses the times when JavaScript fails creating unhappy users.

What are the rules of thumb to avoiding high CPU time?

Reduce, Monitor, Work with Vendors, Performance budgets

What does CPU measure?

How long it takes for JavaScript to settle on a page.

What does Speedcurve do?

Synthetic and real user monitoring

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