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

mirisuzanne

@-webkit-keyframes bgcolor { 0% { background-color: #ffccf2; }
  50% { background-color: #ccffcc; }
  100% { background-color: #ccffff; } }

@-moz-keyframes bgcolor { 0% { background-color: #ffccf2; }
  50% { background-color: #ccffcc; }
  100% { background-color: #ccffff; } }

@-ms-keyframes bgcolor { 0% { background-color: #ffccf2; }
  50% { background-color: #ccffcc; }