fs.exists is important

gistfile1.txt

var fs = require('fs');
var path = require('path');
var getSetting;
if ("we can use exists") {
  getSetting = function(fn, cb) {
    (fs.exists || path.exists)(fn, function(exists) {
      if (!exists) {
        return cb(undefined, 'default value');
      }
      fs.readFile(fn, 'utf8', cb);
    });
  };
} else {
  getSetting = function(fn, cb) {
    fs.readFile(fn, 'utf8', function(err, data) {
      if (err.code === 'ENOENT') {
        return cb(undefined, 'default value');
      }
      cb(err, data);
    });
  };
}

getSetting('setting.txt', function(err, value) {
  if (err) {
    console.warn(err);
  } else {
    console.log('value="' + value + '"');
  }
});