Grunt builmap task

buildmap.js

module.exports = function(grunt) {
  var globalOptions = {
    ext: '.map.json',
    resultMap: {
      javascripts: ['js', 'coffee'],
      stylesheets: ['css', 'less']
    },
    relativePath: true
  };
  grunt.registerTask('buildmap', 'Search for build maps and set on config',
    function() {
      var path = require('path'),
        options = grunt.config.get('buildmap'),
        dest = options.hasOwnProperty('dest') ? options.dest : '',
        maps = options.hasOwnProperty('files') ? options.files : [],
        files = [],
        javascripts = {},
        stylesheets = {};
      // Cast objects to array
      if (grunt.util.kindOf(maps) != 'array') {
        maps = [maps];
      }
      // Expand all maps
      grunt.util.recurse(maps, function(map) {
        map = path.join(map, '**/*' + globalOptions.ext)
        files.push(grunt.file.expand(map));
      });
      // Read each map and set on the right place
      grunt.util.recurse(files, function(file) {
        var fileName = path.basename(file.replace(/\.map\.json$/gi, '')),
          fileExt = path.extname(fileName),
          dirName = path.dirname(file),

          isCss = file.match(/\.(css|less)\.map\.json$/),
          isJs = file.match(/\.js\.map\.json$/),
          jsonMap = grunt.file.readJSON(file),
          result = {};

        if (isCss) {
          result = stylesheets;
        }
        if (isJs) {
          result = javascripts;
        }
        if (jsonMap.hasOwnProperty('files')) {
          result[path.join(dest, fileName)] = jsonMap.files;
        } else {
          grunt.fail.warn('Missing `files` property at `%s`'.replace('%s',
            path.basename(file)));
          return;
        }
      });
      // Set buildmap on config
      grunt.config.set('buildmap.result.javascripts', javascripts);
      grunt.config.set('buildmap.result.stylesheets', stylesheets);
      // Log
      grunt.log.oklns('Build map completed!')
    }
  );
}

Gruntfile.js

module.exports = function(grunt) {
  grunt.initConfig({
    pkg: grunt.file.readJSON('package.json'),
    buildmap: {
      files: ['<%= source.root %>'],
      dest: '<%= source.dest %>'
    }
  });

  grunt.registerTask('default', ['buildmap'], function() {
    // Buildmap will set two variables into config
    grunt.config.get('buildmap.result.javascripts');
    grunt.config.get('buildmap.result.stylesheets');
  });
}