[winter_blue]

Most search engines (and Yandex too I assume), crawl the static web. So if you have a web page whose content is auto-generated using Javscript, it likely won't be indexed by many search engines. Google has been working on this for a while, but it's definitely a very hard problem (tm) to solve (and computationally expensive too).

[menato]

It's not exactly about parsing JS output: JS output is something which is dedicated for user of webpage.

Ilands interface of site is something dedicated to search engine from the origin and helps to create a new layer between search engine and site.