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
ganked from unreadable scribd doc here: http://cleancoder.posterous.com/what-killed-waterfall-could-kill-agile
Robert C. Martin
20 Nov, 2010
In 1970 a software engineer named Dr. Winston W. Royce wrote a seminal paper entitled Managing the Development of Large Software Systems. This paper described the software process that Royce felt was appropriate for large-scale systems. As a designer for the Aerospace industry, he was uniquely qualified.
He began the paper by setting up a straw-man process to knock down. He described this naïve process as “grandiose”. He depicted it with a simple diagram on an early page of his paper. Then the paper methodically tears this “grandiose” process apart. In the end, Royce proposed a far more nuanced and insightful approach, leaving the reader to giggle at the silliness of the “grandiose” model.