index.js

var ConsoleAppender = require("./appenders/consoleappender.js"),
    util = require('util');


var LoggerModule = module.exports = function() {
  this.regex = /%[ldm]/g

  this.active = true;

  this.filler = "\t";

  this.registeredAppenders = [];

  this.consoleAppender = new ConsoleAppender();

  this.messageFormat = "[%l] %d %m";
}

/**
 * Formats the passed message according to the pattern in `LoggerModule.messageFormat`
 */
LoggerModule.prototype._format = function(message, data) {
  return this.messageFormat.replace(this.regex, function(match) {
    if (match == "%m") {
      return data.message;
    } else if (match == "%d") {
      return new Date().toISOString();
    } else if (match == "%l") {
      return data.level;
    } else {
      return "";
    }
  });
};

LoggerModule.createLogFunction = function(logger, logLevel) {
  return function(message) {
    if (logger.active) {
      var formatted = logger._format(logger.messageFormat, {level:logLevel, message:message});
      if (logger.registeredAppenders.length == 0) {
        logger.consoleAppender.write(formatted + "\n");
      } else {
        logger.goThroughAppenders(formatted + "\n");
      }
    }
  }
}

LoggerModule.prototype.info = function(message) {
  if (this.active) {
    var formatted = this._format(this.messageFormat, {level:"INFO", message:message});
    if (this.registeredAppenders.length == 0) {
      this.consoleAppender.write(formatted + "\n");
    } else {
      this.goThroughAppenders(formatted + "\n");
    }
  }
},

LoggerModule.prototype.error = function(message) {
  if (this.active) {
    var formatted = this._format(this.messageFormat, {level:"ERROR", message:message});
    if (this.registeredAppenders.length == 0) {
      this.consoleAppender.write(formatted + "\n");
    } else {
      this.goThroughAppenders(formatted + "\n");
    }
  }
},

LoggerModule.prototype.warning = function(message) {
  if (this.active) {
    var formatted = this._format(this.messageFormat, {level:"WARNING", message:message});
    if (this.registeredAppenders.length == 0) {
      this.consoleAppender.write(formatted + "\n");
    } else {
      this.goThroughAppenders(formatted + "\n");
    }
  }
},

LoggerModule.prototype.addAppender = function(appender) {
  this.registeredAppenders.push(appender);
},

LoggerModule.prototype.goThroughAppenders = function(message) {
  this.registeredAppenders.forEach(function(appender) {
    appender.write(message);
  });
}

module.exports.appenders = {
  FileAppender : require("./appenders/fileappender")
}


if (require.main === module) {
  var FA = new require("./appenders/fileappender.js");

  var logger = new LoggerModule();

  // At this point no appenders have been added to the logger,
  // so it should fallback to the console
  logger.info("This goes to console only");

  logger.addAppender(new FA("foofoo.log"));

  logger.error("This should only go to file!!");
  logger.warning("And this too");

  var loggerTwo = new LoggerModule();
  loggerTwo.info("This is from the second logger and should only go to the console");

  loggerTwo.metrics = LoggerModule.createLogFunction(loggerTwo, "METRICS");
  loggerTwo.metrics("This is a message for metrics on an application");

  var loggerThree = new LoggerModule();
  loggerThree.active = false;
  loggerThree.info("This should not be printed!!!!!!!!!");
}