Patternslib/logging

Minimal logging framework

Introduction

This is a minimal logging framework for javascript. It implements a subset of the log4javascript API, which itself is inspired by log4j. Since log4javascript is huge (180kB) and our needs were small we wrote this 8kB replacement which still supports configurable log levels and hierarchical loggers.

logging can be used both standalone or as an AMD module. If you do not use AMD the logging API is accessible via a global logging object.

logging.info("Hello, world!");
});

If you are using an AMD system such as RequireJS logging will registered as a module and no globals will be installed.

define(["logging"], function(logging) {
    logging.info("Initialisating MyModule");
});

Configuring through URL

To facilitate debugging you can change the default log level through the URL query string by adding loglevel options.

• http://www.example.com/?loglevel=DEBUG changes the default log level to DEBUG.
• http://www.example.com/?loglevel-inject=DEBUG changes the log level for just the inject pattern to DEBUG.
• http://www.example.com/?loglevel=ERROR&loglevel-inject=INFO changes the standard log level error, but enables messages at the INFO level for the inject pattern.

API reference

logging.Level

This is an object which defines all available logging levels: DEBUG, INFO, WARN, ERROR and FATAL.

logging.setEnabled(enabled)

• enabled (boolean): flag indicating if logging should be enabled

This function disables or enables all logging functionality.

logging.setLevel(level)

• level: new logging level

Use this function to change the logging level. The default level is INFO. To change the level to DEBUG you can use this:

logging.setLevel(logging.Level.DEBUG);

Please note that this only changes the root logging level. You can set a different logging for individual lggers as well:

var log = logging.getLogger("MyModule");
log.setLevel(logging.Level.DEBUG);

logging.getLogger(name)

• name (string): name of the logger

Retrieve, and optionally create, a named logger instance.

The logging object (log in the code example) exposes several methods to log information at various log levels:

• debug is used to log debug messages. There are normally not shown.
• info is used to log informational messages. These are normally not shown.
• warn is used to log warnings. These are normally shown.
• error is used to log errors. There are normally shown.
• fatal is used to log fatal errors. There are normally shown.