An update from Addy Osmani about the impact of JavaScript on the web and performance in 2019, and things you can do to impact it. Interesting because the number one items to pay attention to have changed from the conventional wisdom of a couple years back. Osmani:

One large change to the cost of JavaScript over the last few years has been an improvement in how fast browsers can parse and compile script. In 2019, the dominant costs of processing scripts are now download and CPU execution time.