Run loop is a light wrapper around the requestAnimationFrame API. The run loop is just as it sounds, a run loop. It follows a dynamic timing pattern, with an update and render function callback structure. Objects may subscribe to its callback by calling addCall, and passing a callback and the appropriate callback mask.

Callback mask types available:

• RunLoop.UPDATE_CYCLE
• RunLoop.RENDER_CYCLE

Update calls receive an elapsed time in milliseconds, where the render calls will not.

The order for each loop goes update then render. The elapsed time is only provided to the update call.

requestAnimFrame is a polyfill to support requestAnimationFrame and cancelAnimationFrame across browser. This uses an internally provided performance.now(). If this polyfill is used, performanceNow polyfill does not need to be included, it is already included. Since cancelAnimationFrame was widely unsupported while the requestAnimationFrame was used, a noop will be provided in the event that a cancelAnimationFrame does not exist.

Polyfills the following methods, and allows access via UMD, and appends it to the global space, if necessary:

• requestAnimFrame
• cancelAnimFrame
• performance

performance.now() uses the native Web Timing API, but if it is not supported, it uses Date patterns to polyfill. This includes a timing.navigationStart property. The polyfill does not include any of the events or other features beyond the now() functionality, and will not provide microsecond level resolution when the native API isn't available.