A really simple javascript module to log

simpleLog.js

var log = (function () {
  "use strict";
  var format = require('util').format;

  // Customize levels, but do not name any level: "log" "getLevel" "setLevel"
  var levels = { ERROR: 10, WARN: 20, INFO: 30, DEBUG: 40, TRACE: 50 };

  var currentLevel = 'INFO';
  function doGetLevel() { return currentLevel; }
  function doSetLevel(level) {
    if (!levels[level]) { throw new Error('No such level ' + level); }
    currentLevel = level;
  }

  function doLog(level, otherArgs) {
    if (!levels[level] || levels[level] > levels[currentLevel]) { return; }

    var args = [].slice.call(arguments);
    args.shift();
    console.log(level + ': ' + format.apply(this, args));
  }

  var toRet = { log: doLog, getLevel: doGetLevel, setLevel: doSetLevel };

  Object.getOwnPropertyNames(levels).forEach(function (level) {
    this[level.toLowerCase()] = function () {
      var args = [].slice.call(arguments);
      args.unshift(level);
      return doLog.apply(this, args);
    }
  }, toRet);

  return toRet;
})();


// EXAMPLE

console.log('Log level is: ' + log.getLevel());
log.error('This is an error');
log.warn('This is a warning');
log.info('This is info');
log.debug('This is debug');  // Not seen
log.trace('This is trace');  // Not seen

// Adjust level
log.setLevel('TRACE');
console.log('Log level is: ' + log.getLevel());
log.error('This is an error');
log.warn('This is a warning');
log.info('This is info');
log.debug('This is debug');
log.trace('This is trace');

log.setLevel('WARN');
console.log('Log level is: ' + log.getLevel());
log.error('This is an error');
log.warn('This is a warning');
log.info('This is info'); // Not seen
log.debug('This is debug'); // Not seen
log.trace('This is trace'); // Not seen

// sprintf-style formatting.
log.warn('This is a %s generated at %s in process %d',
         'warning', Date(), process.pid);