console.log wrapper that keeps line numbers and su

Question

How can i write a console log wrapper that:

• Keeping the recorded line number and file name of the log statement intact
• Provides access to all log severity methods (error, log, debug, ...) and shows them in the console as they where logged
• does provide some fallback (for example calls the log method when the browser does not support error)
• can be switched off in a central location, so I can switch off logging for production
• does handle the case that no console exists, and does not throw errors

Since logging in Java Script is so inconsistent, there must be some solution. Implementing it myself is a little bit tedious, but there seems to be no good library.

I currently found this logger that provides all the features, but it does mess up the line numbers. http://benalman.com/projects/javascript-debug-console-log/

Answer 1

There is my own log4javascript, which has its own logging console but also provides a wrapper around console.log. It fulfils all your criteria except keeping line numbers intact, which is impossible to achieve if you're wrapping calls to console.log() etc. in another function.

var log = log4javascript.getLogger("main");
var appender = new log4javascript.BrowserConsoleAppender();
log.addAppender(appender);
log.debug("Hello world");

Answer 2

We had this issue with our log wrapper also and it turns out there is a fantastic, simple workaround using partial function application:

if(DEBUG_ENABLED && (typeof console != 'undefined')) {
    this.debug = console.log.bind(console);
}
else {
    this.debug = function(message) {};
}

With this, your browser will detect the correct line number and file of the source you wanted to log.