My personal Log utility. Has option to set log level.

log.js

var Log = {
  _levelInt: function levelInt() {
    return this._levels.indexOf(this.level);
  },
  _intForLevel: function intForLevel(level) {
    return this._levels.indexOf(level);
  },
  _logForLevel: function logForLevel() {
    if (!console) { return; }

    var args = [].slice.call(arguments);
    var level = args.shift();
    var message = args.shift();
    var method = level === "error" ? console.error : console.log;

    if (this._levelInt() > this._intForLevel(level)) { return; }
    method.apply(console, ["["+ level.toUpperCase() +"] " + message].concat(args));
  },

  debug: function debug() {
    var args = [].slice.call(arguments);
    args.unshift("debug");
    this._logForLevel.apply(this, args);
  },
  info: function debug() {
    var args = [].slice.call(arguments);
    args.unshift("info");
    this._logForLevel.apply(this, args);
  },
  error: function debug() {
    var args = [].slice.call(arguments);
    args.unshift("error");
    this._logForLevel.apply(this, args);
  }
};
Log._levels = ["debug", "info", "error"];
Log.level = "debug";