问题
Are search-bot or spam-bots able to emulate/trigger JavaScript events while they read out the page?
回答1:
No, because search bots fetch a static HTML stream. They aren't running any of the initialization events like init() or myObj.init(), which is in your JavaScript code. They don't load any external libraries like jQuery, nor execute the $(document).ready code nor any of the standard .click() listeners. So unless a search bot author has a specific reason to intentionally build their search bot to trigger or execute <script> blocks which are on the page, they usually won't run JavaScript code.
I've written a search bot. All that I care about is extracting the links & text from the page. However, I don't want to run someone else's client-side calendar component nor video player component. I don't want that JS code to be inserted into my database, where it could end up on the Search Engine Results Page (SERP). So there is no reason to run an eval() command on any code in the <script> blocks, nor trigger any of the initialization events in the JS layer.
When search bots load the HTML DOM, there are usually embedded external .js files in them. So to execute the JS would require parsing out the strings for multiple .js files, then building a concatenator for those files & then trying to execute everything that's been downloaded. That's extra work for a search bot author, for no net gain at all. We simply don't want that JS code to appear anywhere in our SERPs. Otherwise, seeing JS code on the SERP looks like a bad search result. However, bots can see content in <script> tags & are only looking for links to crawl. So that may be why people start to think that bots can execute JavaScript, but they are only really parsing them for their text links.
回答2:
Here’s someone who makes the case that Google is loading pages in a headless WebKit when crawling them to get a chance to index AJAX content and for other reasons. Search bots don’t generally submit forms though.
I’ve taken a look at your site and the protection is entirely client-side. Since an HTML form really is just a description of what key/values to submit to some URL, there’s no reason anyone couldn’t just POST this data with a bot.
Example:
POST /contact
/* ... */
fullname=SO+test&email=test%40example.com&reason=test&message=test
Also, and this is important, you are penalising legitimate visitors this way. There’s all kind of reasons why JavaScript could be blocked, fail to load, or simply not work.
来源：https://stackoverflow.com/questions/9937295/are-search-bots-or-spam-bots-able-to-emulate-trigger-javascript-events