TIMING APIs

Page performance is always an area of concern for web developers. The Performance interface changes that by exposing internal browser metrics through a JavaScript API, allowing developers to directly access this information and do as they please with it. This interface is available through the window.performance object. All metrics related to the page, both those already defined and those in the future, exist on this object.

The performance interface is composed of a number of APIs, most of which have two specification levels:

• High Resolution Time API

  Level 1: https://www.w3.org/TR/hr-time-1/#dom-performance-now

  Level 2: https://www.w3.org/TR/hr-time/

• Performance Timeline API

  Level 1: https://www.w3.org/TR/performance-timeline/#sec-window.performance-attribute

  Level 2: https://w3c.github.io/performance-timeline/#extensions-to-the-performance-interface

• Navigation Timing API

  Level 1: https://www.w3.org/TR/navigation-timing/

  Level 2: https://w3c.github.io/navigation-timing/

• User...