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

sebastianseilund

/**
 * `Ember.MergedArray` is an array that observes multiple other arrays (called source arrays) for changes and includes
 * all items from all source arrays in an efficient way.
 * 
 * Usage:
 * 
 * ```javascript
 * var obj = Ember.Object.create({
 *   people: [
 *      {