commonjs组件--日志打印

// logger = require('logger');
// logger.log_to_console(true);
// logger.log_to_folder('log','_app.log');
// logger.set_log_level('DEBUG');
// logger.info('Happy to be here.');
exports.logger = (function() {
  var that = {};
  that.levels = {
    "TRACE": 0, 
    "DEBUG": 1, 
    "INFO": 2, 
    "WARN": 3,
    "ERROR": 4, 
    "SILENT": 5
  };

  var log_file_path = null;
  var log_file_stream = null;
  var log_level = that.levels.ERROR;
  var log_to_console = true;
  var logfunc = null;

  that.trace = function(msg) {
    var my_level = that.levels.TRACE;
    if (my_level >= log_level) {
      logfunc(msg);
    }
  };
  that.debug = function(msg) {
    var my_level = that.levels.DEBUG;
    if (my_level >= log_level) {
      logfunc(msg);
    }
  };
  that.info = function(msg) {
    var my_level = that.levels.INFO;
    if (my_level >= log_level) {
      logfunc(msg);
    }
  };
  that.warn = function(msg) {
    var my_level = that.levels.WARN;
    if (my_level >= log_level) {
      logfunc(msg);
    }
  };
  that.error = function(msg) {
    var my_level = that.levels.ERROR;
    if (my_level >= log_level) {
      logfunc(msg);
    }
  };
  that.log_to_console = function(true_false) {
    if (true_false) {
      log_to_console = true;
    } else {
      log_to_console = false;
    }
  };
  that.log_to_folder = function(log_folder,basename) {
    var date_string = '';
    var filename = '';
    var now = new Date();
    var pad = null;
    var re = new RegExp(fs.separator + '$');

    pad = function(number) {
      if (number.toString().length < 2) {
        return ('0' + number.toString());
      } else {
        return (number.toString());
      }
    };
    if (!fs.isDirectory(log_folder)) {
      fs.makeTree(log_folder);
      if (!fs.isDirectory(log_folder)) {
        throw(new Error(log_folder + ' is not a directory'));
      }
    }
    if (re.exec(log_folder) === null) {
      log_folder += fs.separator;
    }
    date_string += pad(now.getFullYear());
    date_string += pad(now.getMonth());
    date_string += pad(now.getDate());
    date_string += pad(now.getHours());
    date_string += pad(now.getMinutes());
    date_string += pad(now.getSeconds());
    filename = date_string + basename;
    log_file_path = log_folder + filename;
    log_file_stream = fs.open(log_file_path,'w');
    console.log('logging to ' + log_file_path);

  };
  that.get_log_file_path = function() {
    return log_file_path;
  };
  that.get_log_level = function() {
    var ii = 0;
    var keys = Object.keys(that.levels);
    var length = keys.length;
    var value = null;
    for (ii=0; ii<length; ++ii) {
      value = that.levels[keys[ii]];
      if (value === log_level) {
        return keys[ii];
      }
    }
    return null;
  };
  that.set_log_level = function(level) {
    log_level = that.levels[level.toUpperCase()];
    if (log_level === undefined) {
      log_level = that.levels.SILENT;
    }
  };
  logfunc = function(msg) {
    if (log_level < that.levels.SILENT) {
      if (log_file_stream) {
        log_file_stream.writeLine(msg);
        log_file_stream.flush();
      }
      if (log_to_console) {
        console.log(msg);
      }
    }
  };
  return that;
}());