In addition to performance metrics, LUX (SpeedCurve's Real User Monitoring service) also tracks JavaScript errors on your site. With the increased focus on and activity around improving JavaScript, it's important to track errors to make sure JavaScript enhancements don't break functionality. The LUX JS Errors dashboards helps you monitor and isolate errors.

The LUX JS Errors dashboard shows the total number of errors, as well as the error rate. Showing the error rate is helpful if your traffic has regular peaks and valleys (e.g., weekends) where the number of errors might fluctuate but error rate should remain fairly flat.

This dashboard also lists the Top Errors to help you identify the errors that are most affecting customers. It also shows the distribution of errors across top browsers, regions, and pages. You can click on any error message to drill down on it.

Note that "Script error" is often the most popular error message because this is the default error message for all third party scripts. Browsers don't expose the actual error message for security reasons. This happens for third party scripts, but also for scripts you own that are served from a different domain, such as a CDN. To see the error details you must include the crossorigin SCRIPT attribute and the Access-Control-Allow-Origin response header. Note that after making these changes the "Script error" message might still show up from older browsers.

The details for individual errors makes it easy to find and fix problems. For each error the name of the offending script is given, or "HTML document" if the error occurred in an inline script. The line and column number is also provided to help you track down exactly where the error occured.

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