Do Google or other search engines execute JavaScript?

I am just wondering if Google or other search engines execute JavaScript on your web page. For example, if you set the title tag using JavaScript, does the Google search engine see 开发者_如何转开发that?

There have been some experiments performed for SEO purposes which indicate that at least the big players (Google, for example) can and do follow some simple JavaScript. They avoid sneaky redirects and such, but some basic content manipulation does seem to get through. (I don't have a link handy for Google themselves confirming or denying this, it's just various posts I've come across when dealing with this before.)

However, this is generally considered unreliable. If SEO is being done for any important purpose, don't rely on the spiders indexing much dynamic content.

There's actually a very good (in my opinion, anyway) answer here to a very similar question. What I like about that answer is how it breaks down the steps for generating good, indexable, and best of all maintainable web pages with concerns properly separated. Adhering as much as possible to this process generally results in good SEO, good accessibility, and good design skills in general.

Yes, Google executes Javascript. How much is a moving target.

Google executed some Javascript as early as 2011: http://searchengineland.com/google-can-now-execute-ajax-javascript-for-indexing-99518

This article from 2012 documents some experiments on what Javascript Google did and did not run at the time: http://moz.com/ugc/can-google-really-access-content-in-javascript-really

In May 2014, Google said publicly that they execute Javascript: http://googlewebmastercentral.blogspot.com/2014/05/understanding-web-pages-better.html Although that post says that Google has been getting better, there are no publicly available details on what Javascript Google does and does not execute -- but presumably they are at least as good at it as they were in 2012.

I'm pretty sure they dont. However, you can see for yourself: google have a tool which will show you your page as it sees it as http://www.google.com/webmasters/

if the text is in the onpage javascript, google will see the text. but it will not be seen as the text of the title element.

but hey, this is quite easy to test. just do it. wait two days. if you then google your site with site:.... look whats in the headline. if it's in there then the answer is yes: google sees it, if not: no google doesn't. it's easily testable.

(p.s.: my money is on: no)

We need to remember that JavaScript is client-side language, and always start executing from client-side. If all of titles or contents are via javascript then it'll be output from client-side, and I doubt it'll show up on Google search (meanwhile if outputted on .html, then yes).

If I am correct as of latest, meta tags are "fuel for search-engine", and it have ties to SEO, where it is common robots to be scripted to crawl on your site.