Notes from the Google Webmaster Hangout on 6th May 2016, when John Mueller discusses a wide range of SEO topics including JavaScript encoded affiliate links, AJAX versus HTML pages, and rewriting keyword stuffed title tags.
JavaScript/AJAX Is Not Equivalent To HTML
JavaScript/Ajax sites are not 100% equivalent to normal static HTML pages, but it should be possible to make the pages rank as well.
You should avoid using fragments in URLs, and check to see how the pages look with Fetch and Render.
Nofollow JavaScript Encoded Affiliate Links
Any affiliate links which are added using JavaScript should also be nofollowed.
Google Rewrites Keyword Stuffed Title Tags
Google will rewrite title tags which are keyword stuffed, or are duplicated across a lot of pages, and also to make them appropriate for the device.
Nofollow Links on Syndicated Articles
Syndicating multiple versions of a page on different sites, and then canonicalising to a single page, for the purposes of link building, is not acceptable. John says the links on the duplicates should be nofollowed.
Google Prefers Shorter URLs, But Path Depth Isn’t A Factor
The number of URL paths doesn’t affect PageRank. However if there are 2 pages which are a duplicate, they will prefer the shorter URL.
Multiple Redirects To A Page Will Be Treated Like a 404
URLs which 302 redirect to the home page, or any other page, on any large scale will probably be treated like a 404 and dropped from the index, and pagerank won’t be passed.
Google Doesn’t Index Smartphone URL
Google won’t index smartphone URLs, because they are canonicalised to the desktop version. It will store the connection with the desktop URL so it can be shown in search results.