Summary
Applications monitored by RUM generate JavaScript errors referring to Symbol.iterator when using RUM Agent 1.329 or higher. This is caused by the RUM Agent interacting with code that implements Array.prototype.find incorrectly in other JavaScript on the page.
Problem
Following the release of RUM JavaScript Agent 1.329, some customers have reported encountering JavaScript errors on pages utilising the Array.prototype.find() function. We are seeing errors arise when the front-end code using this function returns an invalid value, i.e. a value that does not satisfy the testing function.
Per the Mozilla documentation, this condition should return undefined not any other value. Returning an invalid value will cause the RUM JavaScript Agent to generate an error, which may affect the page loading.
Resolution
In order to resolve this issue, the other JavaScript code on the page must be modified so that it only returns valid values for this function.
As a temporary solution, you can disable New Real User Monitoring in the application settings.
You can just keep classic RUM enabled.
Note: This will result in the loss of new monitoring for RUM data and no data in all third-generation applications, such as Experience Vitals.
Reccomandation: Please ensure that you implement browser APIs in your JavaScripts in accordance with specification standards, thus avoiding any potential issues with other tools that utilise these APIs, such as Dynatrace New RUM.
What's next
This issue arises in version 1.329 because the New RUM agent introduced functionality that utilises the browser APIs like Array.prototype.find method, which is only available in version 1.329 and above. Therefore, it relies on the correct implementation of the Array.prototype.find method if it is used by other JavaScript on the same page.
Please find a list of all the browser APIs used by Dynatrace New RUM:
The process of identifying all the APIs requiring adjustment implementation can be conducted by performing a health check, as demonstrated below(When new RUM is enabled):
- Open Chrome.
- Open Developer Tools (F12).
- Navigate to the affected web application.
- Open Console and run:
await dynatrace.loadDebugTools();
dynatrace.debugtools.runHealthCheck();
If this article did not help, please open a support ticket, mention that this article was used and provide the following in the ticket:
