Does Schema.org markup work if markup is dynamically built with JavaScript?

Question

I have a page where some events are dynamically loaded by reading some JSON with JavaScript. I build a div for every event with the Event Schema.org markup.

Google's testing tool doesn't read this markup. Is it because of an error in the markup, or is it because of the dynamic loading?

The HTML code of one Event is:

<div class="evento well" itemscope itemtype="http://schema.org/Event">
   <meta itemprop="startDate" content="2015-03-20T20:00:00.000Z">
   <meta itemprop="endDate" content="2015-01-21T20:00:00.000Z">
   <div class="dataEvento">
      <div class="dayWeekEvento">venerdì</div>
      <div class="dayNumEvento">20</div>
      <div class="monthEvento">Marzo</div>
   </div>
   <div class="datiEvento">
      <div class="oraEvento">ore 21:00</div>
      <div class="titoloEvento"><span itemprop="name">Titolo evento</span></div>
      <div class="luogoEvento" itemprop="address" itemscope="" itemtype="http://schema.org/PostalAddress"><a href="https://www.google.it/maps/place/Milano" target="_blank"><span class=" glyphicon glyphicon-map-marker" aria-hidden="true"></span> <span itemprop="addressLocality">Milano</span></a></div>
   </div>
</div>

Answer 1

Google’s documentation only mentions that they can consume dynamically added structured data if the syntax JSON-LD is used:

Also, Google can read JSON-LD data even when it is dynamically injected into the page's contents, such as by Javascript code or embedded "widgets".

This does not necessarily mean that they can’t read it in case of other syntaxes (like Microdata or RDFa), but at least they don’t document it.

That their testing tool doesn’t read it may or may not mean something (it could be that the tool doesn’t handle this but their internal system does). However, there should be no issue with your actual markup, as you can easily test it yourself by pasting your markup instead of entering your URL.

Answer 2

If you're having trouble validating schema markup with the Google testing tool, you can create the json-ld snippet with JS, which also allows you to manipulate the data if needed like:

<script> 
    (function(){
       var data = {
            "@context": "http://www.schema.org",
            ...
        }
        var script = document.createElement('script');
        script.type = "application/ld+json";
        script.innerHTML = JSON.stringify(data);
        document.getElementsByTagName('head')[0].appendChild(script); 
    })(document);
</script>

Answer 3

It depends on what type of markup it is. From Google:

JSON-LD is supported for all Knowledge Graph features, sitelink search boxes, Event Rich Snippets, and Recipe Rich Snippets; Google recommends the use of JSON-LD for those features. For the remaining Rich Snippets types and breadcrumbs, Google recommends the use of microdata or RDFa.

It should work but I know people have reported problems with the testing tool.