A JavaScript error means that some code (a script) running in your shop encountered a problem that it could not recover from. Whether this error impacted your shopper's experience depends on what the code does.
In most cases. a JavaScript error will not affect the shopper's experience.
In some cases though, a JavaScript error can indicate a more serious problem such as a broken app or theme widget that could be causing you sales.
To diagnose the problem, visit your shop then open your browser's 'JavaScript Console'.
- In Chrome, follow the steps here: https://www.techonthenet.com/js/open_console_log.php
- In Safari, follow the steps here: https://support.awesome-table.com/hc/en-us/articles/360001785620-Using-the-Debug-Console-in-Safari-to-identify-errors
Once you've opened the JavaScript console, look for the lines in red. Some of those may be JavaScript errors and will contain both an error message and name of the file causing the error. These can then be passed to your web developer for help resolving.