handlebars.js/tests/bench/dist-size.js

var async = require('neo-async'),
  fs = require('fs'),
  zlib = require('zlib');

module.exports = function(grunt, callback) {
  var distFiles = fs.readdirSync('dist'),
    distSizes = {};

  async.each(
    distFiles,
    function(file, callback) {
      var content;
      try {
        content = fs.readFileSync('dist/' + file);
      } catch (err) {
        if (err.code === 'EISDIR') {
          callback();
          return;
        } else {
          throw err;
        }
      }

      file = file.replace(/\.js/, '').replace(/\./g, '_');
      distSizes[file] = content.length;

      zlib.gzip(content, function(err, data) {
        if (err) {
          throw err;
        }

        distSizes[file + '_gz'] = data.length;
        callback();
      });
    },
    function() {
      grunt.log.writeln(
        'Distribution sizes: ' + JSON.stringify(distSizes, undefined, 2)
      );
      callback([distSizes]);
    }
  );
};