All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.
Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.
elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent
I have always struggled with getting all the various share buttons from Facebook, Twitter, Google Plus, Pinterest, etc to align correctly and to not look like a tacky explosion of buttons. Seeing a number of sites rolling their own share buttons with counts, for example The Next Web I decided to look into the various APIs on how to simply return the share count.
If you want to roll up all of these into a single jQuery plugin check out Sharrre
Many of these API calls and methods are undocumented, so anticipate that they will change in the future. Also, if you are planning on rolling these out across a site I would recommend creating a simple endpoint that periodically caches results from all of the APIs so that you are not overloading the services will requests.
A curated list by Eric Elliott and friends. Suggest links in the comments below.
This is a very exclusive collection of only must-have JavaScript links. I'm only listing my favorite links. Nothing else makes the cut. Feel free to suggest links if you think they're good enough to make this list. The really curious should feel free to browse the comments to find other links. I can't guarantee the quality of links in the comments.
Some of these links are affiliate links, meaning that if you make a purchase, I might earn a little money. This has absolutely no bearing on whether or not links make the list. None, whatsoever. However, it does allow me more resources to fight poverty with code. Every little bit counts.