Website Optimization - Page Load Time & DOM manipulations

Question

Just wondering whether JavaScript execution i.e. for DOM Manipulation is taken into account by Tools like http://tools.pingdom.com/, Google Analytics that calculate a Web pages Load Time obviously there is a distinction between Download Time & Load Time? Does Load time include when JS has finished executing?

Answer 1

Good question! The short answer is no.

JavaScript "load time" is dependent on complexity, latency to fetch files (CDNs, etc.), and other browser-dependent factors.

A tool like Google Analytics receives data about the page (through tracking pixels), but isn't the same as a bonafide web browser.

A tool like Pingdom or Pingometer which monitors a site either does a HEAD or GET request to the page.

In the case of a HEAD request, no code is downloaded or executed -- only headers.

In the case of a GET request, code is actually downloaded (and a factor for load time) but not executed.