A template for a typical transformation for gulp

myTransformation.js

const through = require('through2'),
      PluginError = require('gulp-util').PluginError;

module.exports = function myTransformation(options) {
  if(!options) {
    options = {};
  }

  return through.obj(function (file, enc, cb) {
    if (file.isNull()) {
      // return as is
      cb(null, file);

    } else if (file.isBuffer()) {
      try {
        const content = file.contents.toString('utf8');
        // do any transformation
        file.contents = new Buffer(content, 'utf8');
        cb(null, file);
      }
      catch (err) {
        throw new PluginError('my-transformation', err);
      }

    } else if (file.isStream()) {
      throw new PluginError('my-transformation', 'Streams are not supported!');
    }
  });
};