October 2013 web platform update

Now available in Firefox
Limited availability

Array find() and findIndex(): The find() and findIndex() methods of arrays and typed arrays search an array for the first item that satisfies a test function. Learn more.
Array.of(): The Array.of() and typed array .of() static methods create new arrays from the values of any number of arguments. Learn more.

Array.of(): The Array.of() and typed array .of() static methods create new arrays from the values of any number of arguments. Learn more.

calc(): The calc() CSS function computes mathematical expressions such a calc(100%/3 - 1em). Learn more.
requestAnimationFrame(): The requestAnimationFrame() method schedules a function that runs before the next repaint. You can use it to animate content with JavaScript. Learn more.
Speech synthesis: The SpeechSynthesis API converts text into audio using a synthetic voice. Learn more.
Viewport units: The vw, vh, vmin, and vmax CSS viewport units are relative to the size of the viewport, and are used to size elements in relation to the viewport's dimensions. Learn more.
WebVTT regions: WebVTT regions set the areas of the video where captions or subtitles should be rendered, such as placing roll-up captions used for live captions. Learn more.