You can transpile server-side Node.js code using grunt-traceur in the same manner you compile client-side code. In order to use this Grunt task for Node.js source code, you will need to set the module flag to commonjs.

Here's an example Grunt config:

  traceur: {
    options: {
      experimental: true,
      modules: 'commonjs'
    server: {
      files: [{
        expand: true,
        cwd: 'src/server',
        src: ['**/*.js'],
        dest: 'build/server'

When the traceur grunt task is run, it will output the ES5 version of your source to the output directory.