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Getting started with JavaScript logging

Demos and sample code

The Basics

After you have installed JSNLog, add this to your JavaScript code to send a log message to your server side log:

JL().fatal("log message");

JL() returns a nameless logger, called the root logger. In your server side log, it will be called ClientRoot.

You can log objects as well:

JL().fatal({"i": 5, "j": 6});

Named loggers

To make it easier to track where in your code the message was logged, give your loggers names. For example:

JL("function1.logger1").warn("log message");

Message severity

JSNLog is very similar to Log4J / Log4Net. It uses the same severities: TRACE, DEBUG, INFO, WARN, ERROR or FATAL.

For example:

JL().trace("a trace message");

Set logger options

JSNLog has many features that help you reduce log traffic by only logging useful information. For example:

var logger = JL();
    "userAgentRegex": "MSIE 7|MSIE 8"

logger.trace("Only IE7 and IE8 will send this message.");

Log exceptions in a try-catch block

JSNLog logs uncaught exceptions for you out of the box. You can add to this by catching exceptions in a try-catch block and then logging the exception (details):

try {
    ... dodgy code
} catch (e) {
    JL().fatalException("something went wrong!", e);

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