There are still a few cases where you won't be in control of the caching behavior. For example, if you render a page, then navigate to a third party website, and the user clicks back. Applications that render HTML on the server and then modify it on the client are at particular risk of this subtle bug:

Form submissions aside, if we were to design any modern web application with only hyperlinks, we'd end up with fully functional back/forward navigation.

Consider, for example, the typical "infinite pagination scenario". The typical way it's implemented involves capturing the click with JavaScript, requesting some data / HTML, injecting it. Making the history.pushState or replaceState call is an optional step, unfortunately not taken by many.

And this is why I use the word "break". With the simpler model the web proposed initially, this situation was not in the picture. Every state transition relied on a URL change.

The flip side of this is that new opportunities emerge for enhancing history now that we can control it with JavaScript.

And in 2010 they introduced Instant Search, which puts JS front and center by skipping the page refresh altogether and transitioning to the "search results" layout as soon as you press a key as we saw above.

Another prominent example of layout adaptation is most likely in your pocket. Ever since the early days, iPhone OS would request app authors to provide a default.png image that would be rendered right away, while the actual app was loading.

This is a writeup based on a presentation I gave at BrazilJS in August 2014. It builds on some of the ideas I've been blogging about recently related mostly to UX and performance.

I want to introduce 7 actionable principles for websites that want to make use of JavaScript to control their UI. They are the result of my experience as a web developer, but also as a long-time user of the WWW.

JavaScript has undeniably become an indispensable tool for frontend developers. Its usage is now expanding into other areas like servers and microcontrollers. It's the language of choice for introducing computer science concepts by prestigious universities.