I’ve been thinking about Scott Jehl’s “simplest way to load external CSS asynchronously” technique. I’m interested in its use of an inline (onload) event handler for running JavaScript-based enhancements in the <head>, in the context of some broader ruminations on how best to progressively enhance UI elements with JavaScript (for example adding toggle show/hide) without causing layout jank.
One really interesting aspect of using inline event handlers to apply enhancements was highlighted by Chris Ferdinandi today: as JavaScript goes, it’s pretty resilient.
Because we’re dealing with an HTML element directly in the document, and because the relevant JS is inline on that element and not dependent on any external files, the only case where the JS won’t run is if someone has JS completely turned off – a sub-1% proportion. The other typical JavaScript resilience pitfalls – such as network connections timing out, CDN failure and JS errors elsewhere blocking your code from running – simply don’t apply here.