carmilso/tracer-debug

tracer-debug

This program is basically a wrapper for tracer, a logging library for node.js.

With tracer-debug all output can be conveniently hidden at will, e.g. when running in production environments. For instance, you can choose to display output when NODE_ENV is set and is different from production (default behavior).

Different configuration options are available, although you'll be (hopefully) ok with the default ones:

var TracerDebug = require('tracer-debug')
  , logger      = new TracerDebug()
  ;

Options

This program accepts the same options as tracer (see https://www.npmjs.com/package/tracer), plus the following ones:

displayWhen

This option controls when should output messages be shown. To display output messages, you must specify any "truthy" value or an expression that evaluates to true. Examples:

var TracerDebug = require('tracer-debug');

// This will show output messages when no environment is set.
var myLogger = new TracerDebug({
  displayWhen: typeof process.env.NODE_ENV === 'undefined'
});

// This will show output messages when running in a development environment.
var otherLogger = new TracerDebug({
  displayWhen: process.env.NODE_ENV === 'development'
});

myLogger.log("._.");
otherLogger.log("*_*");

By default, all messages are not shown when running in production, i.e. displayWhen equals to typeof process.env.NODE_ENV === 'undefined'.

stackTrace

If stackTrace is set to true, the full stack trace will be shown. Different levels of verbosity are possible, e.g. if stackTrace is set to 1, the first line of the stack trace will be shown after the output message; if stackTrace is set to 2, the first two lines of the stack trace will be shown after the output message; and so on. Examples:

var TracerDebug = require('tracer-debug');

// This will display the full stack trace (from caller file).
var myLogger = new TracerDebug({
  stackTrace: true
});

// This will display the first 3 lines of the stack trace.
var otherLogger = new TracerDebug({
  stackTrace: 3
});

myLogger.log("hello");
otherLogger.log("world");

Example

Do npm install and create the file test.js:

var TracerDebug = require('tracer-debug');

var logger = new TracerDebug({
  format: "logger/{{title}}: {{message}}",
  stackTrace: true,
  singleton: true
});

logger.log(42);

// In singleton mode, the output is the same as in the previous `logger` instance.
// If we don't use `singleton: true` a brand new instance is created.
var logger2 = new TracerDebug({ singleton: true });
logger2.log(42);

// Notice the stack trace.
(function test() {
  logger.trace('An object:', { foo: 1, bar: { a: 2, b: 3 } });
})();

// The following examples are just to show the colored output.
// It also showcases how native types are displayed.
logger.debug(true, false);
logger.info(1/0, 0/0);
logger.warn(null, undefined);
logger.error(new Error("An error has been thrown."));

// Let's manipulate the original tracer instance.
logger.transport.setLevel('warn');
logger.log('This message should not be shown!');
logger.warn('hello %s! %j', 'world', { foo: 1 });
// Notice that in singleton mode any modification is populated to other instances.
logger2.log('This message should not be shown!');

And then call it as NODE_ENV=debug nodejs test.js or NODE_ENV=development nodejs test.js to see the output. Notice that if you call it as NODE_ENV=production nodejs test.js or simply nodejs test.js, no output is shown.