The Crawling Process
What Happens To My JS Then?
Chrome 41, which is the latest version of Googlebot (Google's user agent, to be clear) doesn't crawl any JS library but, instead, it renders the resources to then index the whole package of data. To clarify, the process for what concerns a page which doesn't have any form of JS installed is Crawl and then Index, whilst for a page that has any form of JS installed (jQuery, Node, React) the user agent will first crawl the page, to then render the non-HTML and CSS resources and, finally, index the whole package.
What's The Best Approach For JS SEO?
The Mobile Matter