jslogger

Lightweight framework-agnostic Javascript logger.

Usage:
Include this in your doc...
<script type="text/javascript" src="/path/to/jslogger.js"></script>

Log from your app:
jslogger.debug("Hey I'm in the foo function, bar is " + bar);

or
try {
  ...
} catch (e) {
  jslogger.error("Failed to create widget, exception thrown.", e);
}

Call your app with this query string (using the desired level param)...
http://mydevapp:3000/things?showLog=true&level=debug|info|error_message