Javascript redirects -- what are the SEO pitfalls?

[FR123]

Q: Is it dangerous (SEO fallout) to use javascript redirects?

Tech team built a browser side tool for me to easily redirect old/broken links. This is essentially a glorified 400 page -- pops a quick message that the page requested no longer exists and that we're automatically sending you to a page that has the content you are looking. Tech team does not have the bandwidth to handle this via apache and this tool is what they came up with for me to deliver a better customer experience.

Back story: very large site and I'm dealing with thousands of pages that could/should/need to be redirected. My issue is incredibly similar to what Rand mentioned way back in a post from 2009: Are 404 Pages Always Bad for SEO? We've also decided to let these pages 404 and monitor for anything that needs an apache redirect. Tool mentioned above was tech's idea to give me "the power" to manage redirects.

What do you think?

[customerparadigm.com]

My $0.02 is that javascript might work for your site, but it's not going to give you the benefits that 301 redirects will offer to you.

According to Google's Official Webmaster Central Blog, as of May 23, 2014, Google is able to execute Javascript:
http://googlewebmastercentral.blogspot.ca/2014/05/understanding-web-pages-better.html

That said, if you have your javascript or CSS in separate files, and are blocked with robots.txt, according to Google, they won't be able to execute it. And according to the post, they can't process all javascript.

It's not a bad thing to have 404 pages for pages that you want to kill off and let die. If you do have important inbound links, though, it's better to 301 redirect them and keep 85% of the link strength. More backup on this:

According to Rand Fishkin's Moz blog writeup, Are 404 Pages Always Bad for SEO?
http://moz.com/blog/are-404-pages-always-bad-for-seo

"When faced with 404s, my thinking is that unless the page:

A) Receives important links to it from external sources (Google Webmaster Tools is great for this)
B) Is receiving a substantive quantity of visitor traffic
and/or C) Has an obvious URL that visitors/links intended to reach

It's OK to let it 404."

According to Moz's Redirection SEO Best Practice:
http://moz.com/learn/seo/redirection
... you want to use a 301 redirect to indicate that the content has moved permanently.

I hope this helps!

-- Jeff