Convert url image ref into inline base 64 in css with nodejs

gistfile1.js

var css = 'insert lots of css here';

var files = {};
css = css.replace(/url\((\S*)\.(png|jpg|jpeg|gif)\)/g, function(match, file, type)
{
  var fileName = file + '.' + type;
  var base64 = fs.readFileSync(fileName).toString('base64');
  if (typeof(files[fileName]) !== 'undefined') {
    console.log('Warning: ' + fileName + ' has already been base64 encoded in the css');
  }
  files[fileName] = true;
  return 'url("data:image/' + (type === 'jpg' ? 'jpeg' : type) + ';base64,' + base64 + '")';
});