Client-side logging and debugging
Often, you use the trace() method
when you debug applications to write a checkpoint message on the
client, which signals that your application reached a specific line
of code, or to output the value of a variable.
The debugger version of Flash Player has two primary methods
of writing messages that use trace():
The global trace() method. The global trace() method
prints Strings to a specified output log file. For more information,
see Using the global trace() method.
Logging API. The logging API provides a layer of functionality
on top of the trace() method that you can use with
your custom classes or with the data service APIs. For more information,
see Using the logging API.