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

asfaltboy

/*
 * Copyright (C) 2015 Pavel Savshenko
 * Copyright (C) 2011 Google Inc.  All rights reserved.
 * Copyright (C) 2007, 2008 Apple Inc.  All rights reserved.
 * Copyright (C) 2008 Matt Lilek <webkit@mattlilek.com>
 * Copyright (C) 2009 Joseph Pecoraro
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:

branneman

JavaScript knowledge

• Operators, operands, operator precedence (unary, binary, ternary)
• Dynamic Type system: types and conversion
  • Value type vs. Reference type
• Expression vs. Statement
• Scope
• Hoisting
• Overloading
• Prototypal inheritance vs. Classical inheritance
• Instancing