Here are some tools to find JS errors.
Anatomy, an access analysis tool that "visualizes" Google Analytics, has not only information on analysis such as access indicators and user traffic lines, but also screen captures of pages and resource information. So you can check for JS errors in the page.
- 1.Display page information tab
2. Click the [JS error] button
3.Tile turns red on pages with JS error
4. Right-click the tile and click [Display detailed information of page].
- 5. Click [Resource] on the detailed information page
With this alone, you can check the page where the JS error has occurred and the resource where the error has actually occurred.
If you have any concerns about your Google Analytics settings, such as not being able to measure the pages you care about, there is also a service that can diagnose the settings of Google Analytics.