Total Browser Processing Time
Time To First Layout
Layout Rendering Time
CSS Processing Time
CSS Calculations
Javascript Execution Time
Javascript Event Listeners
JavaScript Execution Time
Target Less than 1.5 seconds
An indicator that the page is doing too much 'thinking and watching'
Javascript functions must all be processed, stored in memory, and executed according to either 1) loading priority, or 2) defined method execution, i.e. funciton calls from script files or tags.
Javascript can be included in the initial page HTML payload, loaded from a file.js, or injected by a third-party application.
Javscript can take considerable browser resources to execute. An often overlooked concern with pages loaded with javascript, is the tendency for javascript functions to cause re-layouts and re-calculations of DOM elements. This is a silent killer for page performance.
We should assume that time spent in javascript execution can cause degraded scroll and click performance, giving pages that 'sticky' feeling.
