Implementing Enhanced SEO Option 2: on_change Callback

This article correlates to PowerReviews' Enhanced SEO: Option 2.

The on_change callback function exposes a method to provide structured data for Review schemas. This callback function is a direct replacement for the on_render function -- you cannot have both on one page.

How to Enable

Define the callback function and check for the presence of reviews.

on_change: function(config, data) {
       if(config.component === 'ReviewList') {
           // Check for the presence of reviews
            if(data.review_count > 0 && (data.reviews).length > 0) {
                 var reviews = [];

If there are reviews, dynamically create your Review schema objects with the data exposed in the "data" parameter.

// Dynamically create an object for the Reviews schema
for (var i = 0; i <= ((data.reviews).length)-1; i++)  
  var pwrReview = data.reviews[i];
  var review = {
     "@type": "Review",
     "name": pwrReview.details.headline,    
     "reviewBody": pwrReview.details.comments,
     "datePublished": new Date(pwrReview.details.created_date).toISOString(),
Date(pwrReview.details.created_date).toISOString(),
     "author": {    
     "@type": "Person",
     "name": pwrReview.details.nickname   
     },
     "reviewRating": {    
       "@type": "Rating",
       "ratingValue": pwrReview.metrics.rating
     } 
   };
   if(pwrReview.details.location && 
(pwrReview.details.location).toLowerCase() != 'undisclosed') {
     review["locationCreated"] = {
       "@type": "AdministrativeArea",
       "name": pwrReview.details.location
     };
   }
   reviews.push(review);
   }

Append the Review schemas to the existing Product schema.

// Attach the Review schemas to the existing Product schema
  var scriptTag = document.getElementById('productschema');
  var scriptTagObject = JSON.parse(scriptTag.innerHTML);
  for (var i = 0; i <= (scriptTagObject.length-1); i++) {
    if(scriptTagObject[i]) { 
      scriptTagObject[i]['review'] = reviews;
     } 
   }
   scriptTag.innerHTML = JSON.stringify(scriptTagObject);
}

If there are no reviews available (pagination, filtering, etc.), remove the Review schema.

// If no reviews available due to filtering/pagination/search
// remove review object from each product variation group in
// the product schema
if((data.reviews).length == 0) {
  var scriptTag = document.getElementById('productschema');
  var scriptTagObject = JSON.parse(scriptTag.innerHTML);
  for (var i = 0; i <= (scriptTagObject.length-1); i++) {
    if(scriptTagObject[i]) {
      delete scriptTagObject[i]['review'];   
    }
  }
  scriptTag.innerHTML = JSON.stringify(scriptTagObject);
}

Full Code:

<script>
on_change: function(config, data) {
	if(config.component === 'ReviewList') {
	// Check for the presence of reviews
	if(data.review_count > 0 && (data.reviews).length > 0) {
	  var reviews = [];	
	  // Dynamically create an object for the Reviews schema
	  for (var i = 0; i <= ((data.reviews).length)-1; i++) {
	    var pwrReview = data.reviews[i];
	    var review = {
		"@type": "Review",
		"name": pwrReview.details.headline,
		"reviewBody": pwrReview.details.comments,
		"datePublished": new 
Date(pwrReview.details.created_date).toISOString(),
		"author": {
		   "@type": "Person",
		   "name": pwrReview.details.nickname
		},
		"reviewRating": {
		   "@type": "Rating",
		   "ratingValue": pwrReview.metrics.rating
		}
	    };
	    if(pwrReview.details.location && 
(pwrReview.details.location).toLowerCase() != 'undisclosed') {
		review["locationCreated"] = {
		  "@type": "AdministrativeArea",
		  "name": pwrReview.details.location
		};
	    }
	    reviews.push(review);
	  }
	  // Attach the Review schemas to the existing Product schema	
	  var scriptTag = document.getElementById('productschema');		
	  var scriptTagObject = JSON.parse(scriptTag.innerHTML);
	  for (var i = 0; i <= (scriptTagObject.length-1); i++) {
	    if(scriptTagObject[i]) {
	      scriptTagObject[i]['review'] = reviews;
	    }
	  }
	  scriptTag.innerHTML = JSON.stringify(scriptTagObject);
	  }
	  // If no reviews available due to filtering/pagination/search
	  // remove review object from each product variation group in the product schema
	  if((data.reviews).length == 0) {
	    var scriptTag = document.getElementById('productschema');
	    var scriptTagObject = JSON.parse(scriptTag.innerHTML);
	    for (var i = 0; i <= (scriptTagObject.length-1); i++) {
	      if(scriptTagObject[i]) {
		delete scriptTagObject[i]['review'];
	      }
	      }
	      scriptTag.innerHTML = JSON.stringify(scriptTagObject);
	    }
	}
    }
</script>