we are creating client side JavaScript applications for customer with a closed network. Some of our customer complaining about unexpected behavior of our applications. But these problems are hard to tackle, because we don’t have direct access to the devices and the customer is not able to store the web browser log files just in this moment (plus, we are developing for mobile devices…).

Is there any software solution that can send us the JavaScript log files to a backend, so that we can check the logs after we got the problem reports?

What I found so far was only some cloud based services and 10 years old abandoned projects on github.
Maybe I missed some nice project or some good ideas to solve this problems.