Observing an adslot with MutationObserver API.

Introduction

In the world of ad tech, ensuring that ad slots function correctly is essential for a smooth user experience and accurate analytics. Observing changes in ad slots can provide valuable insights into how they behave under different conditions. The MutationObserver API is a powerful tool for detecting changes in the DOM, and when combined with Requestly’s insert script feature, you can efficiently monitor ad slots in real time without altering your production code.

In this post, I’ll show you how to use Requestly to insert a script that leverages the MutationObserver API to observe ad slots for any mutations.

Why Use Requestly?

Requestly is a versatile tool that allows you to modify, redirect, or insert scripts into HTTP requests and responses. This makes it an excellent choice for testing and debugging web applications. By using Requestly to insert custom JavaScript, you can monitor dynamic elements on your web pages, such as ad slots, to ensure they perform as expected.

Setting Up Mutation Observations for Ad Slots with Requestly

1. Install Requestly

First, install the Requestly extension from the Chrome Web Store or Requestly’s official website. After installation, you’ll see the Requestly icon in your browser.

2. Set Up an Insert Script Rule

The Insert Script Rule in Requestly allows you to inject custom JavaScript into web pages, making it ideal for running scripts like the MutationObserver. This feature helps you monitor changes to ad slots and other dynamic elements without modifying the live codebase.

Here’s how you can insert a script to observe ad slots:

1. Open Requestly: Open Requestly app .
2. Create a New Rule: Click on New Rule and choose Insert Script
3. Enter the URL Pattern: Add the URL pattern for the pages where you want to monitor ad slots. This specifies where the script will be injected.

4. Add the Script: Paste your JavaScript code that uses MutationObserver to detect changes in ad slots. Here’s an example script:
   

   
   // Select the node that will be observed for mutations
   var targetNode = document.getElementById('<ad_ID>');
   
   // Options for the observer (which mutations to observe)
   var config = { attributes: true, childList: true };
   
   // Callback function to execute when mutations are observed
   var callback = function (mutationsList) {
       for (var mutation of mutationsList) {
           if (mutation.type == 'childList') {
               // Console log to show when child nodes are added or removed
               //console.log('A child node has been added or removed.');
           }
           else if (mutation.type == 'attributes') {
               // Log attribute changes to the console
               console.info('ADTECH: MutationObserver - mutationsList ->', mutationsList);
               //console.log('The ' + mutation.attributeName + ' attribute was modified.');
           }
       }
   };
   
   // Create an observer instance linked to the callback function
   var observer = new MutationObserver(callback);
   
   // Start observing the target node for configured mutations
   observer.observe(targetNode, config);
   
   // Later, you can stop observing
   //observer.disconnect();
   

5. Save the Rule: Click ‘Save’ to apply the rule. Ensure it is activated by toggling the switch to the 'On' position.

Conclusion

Observing ad slots for mutations using the MutationObserver API with Requestly’s insert script feature is a straightforward and effective way to monitor changes in real time. Whether you’re debugging ad slot behavior or ensuring content accuracy, Requestly provides the tools you need to gain valuable insights without disrupting your production environment.

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