JSON-LD GTM Tag

json-ld-gtm.html

<script>
  (function(){
    var data = {
        "@context": "http://schema.org",
        "@type": "BlogPosting",
        "mainEntityOfPage": {
            "@type": "WebPage",
            "@id": {{Page URL}}
        },
        "headline": {{SCHEMA - Article Headline}},
        "image": {
          "@type": "ImageObject",
          "url": {{SCHEMA - Article Image}},
          "height": 413,
          "width": 1159
        },
        "datePublished": {{SCHEMA - Article datePublished}},
        "author": {
            "@type": "Organization",
            "name": {{SCHEMA - Author Name}}
        },
        "publisher": {
            "@type": "Organization",
            "name": "City of Philadelphia",
            "logo" : {
                "@type": "ImageObject",
                "url": "http://cityofphiladelphia.github.io/patterns/images/city-of-philadelphia.png",
                "height": 126,
                "width": 449
             }
        },
        "description": {{SCHEMA - Article Description}}
    }
   
    var dateModified = {{SCHEMA - Article dateModified}};
    
    if(dateModified){
      data.dateModified = dateModified;
    } else {
      data.dateModified = {{SCHEMA - Article datePublished}};
    }
  
    var script = document.createElement('script');
    script.type = "application/ld+json";
    script.innerHTML = JSON.stringify(data);
    document.getElementsByTagName('head')[0].appendChild(script); 
  })(document);
</script>