paulirish

What forces layout / reflow

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.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

Dither

// JavaScript function for converting simple XPath to CSS selector.
// Ported by Dither from [cssify](https://github.com/santiycr/cssify)
// Example: `cssify('//div[@id="girl"][2]/span[@class="body"]//a[contains(@class, "sexy")]//img[1]')`

var sub_regexes = {
    "tag": "([a-zA-Z][a-zA-Z0-9]{0,10}|\\*)",
    "attribute": "[.a-zA-Z_:][-\\w:.]*(\\(\\))?)",
    "value": "\\s*[\\w/:][-/\\w\\s,:;.]*"
};