3

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](http://www.kellegous.com/j/2013/01/26/layout-performance/), and is common performance bottleneck.

5

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.