Can Google Crawl JavaScript and AJAX?

JavaScript is a language that is used by developers to enhance the web experience.

JavaScript is used to handle things like:

• Animations (e.g. banners sliding / fading)
• Drop down menus
• Error / Validation messages
• Popups
• Slide shows
• Loading remote content (without forcing the entire page to reload).

It is very rare to find a page or website that doesn't use JavaScript these days.

However how does using JavaScript affect Google? Especially does Google "follow" JavaScript?

Imagine this, you have a button on your home page that says "click here for further information". This button (when clicked) will activate a "popup" (or modal) window that loads additional content.

This is great for user experience (in that we are not overwhelming the user with info).

But will Google "follow" this and read this additional content (like a real person)?

In most cases yes. Since 2015: Google has been asking web developers to not block JavaScript resources from Google robots (spiders). As part of this Google has indicated that they do read JavaScript to some extent. 

Best practice

It is still best practice (from an SEO perspective) to present your most important information visually and "in-page" so users can see it without use of JavaScript and without having to click on a button. However, we now know that Google will "follow" JavaScript and crawl this additional content.