A Grunt string-replace task option for replacing CSS url() paths.

string-replace.js

{
  pattern: /url\((.*?)\)/ig,
  replacement: function (match, p1, offset, string) {
    var path, pathParts, pathLength, filename, newPath;
    path = p1.replace(/["']/g,''); // Removes quotation marks if there are any
    pathParts = path.split('/'); // Splits the path so we can find the filename
    pathLength = pathParts.length;
    filename = pathParts[pathLength-1]; // The filename is the last item in pathParts

    // Rewrite the path based on the file type
    // Note that .svg can be a font or a graphic, not sure what to do about this.
    if (filename.indexOf('.eot') !== -1 ||
        filename.indexOf('.woff') !== -1 ||
        filename.indexOf('.ttf') !== -1 ||
        filename.indexOf('.svg') !== -1)
    {
      newPath = 'url("../fonts/'+filename+'")';
      grunt.verbose.ok('Replaced:',match,'\n    with:',newPath);
      grunt.verbose.writeln('');
      return newPath;
    } else if (filename.indexOf('.png') !== -1 ||
        filename.indexOf('.gif') !== -1 ||
        filename.indexOf('.jpg') !== -1)
    {
      newPath = 'url("../img/'+filename+'")';
      grunt.verbose.ok('Replaced:',match,'\n    with:',newPath);
      grunt.verbose.writeln('');
      return newPath;
    } else {
      grunt.verbose.warn('No filetype matches for:',match,'\n');
      grunt.verbose.writeln('');
      return match;
    }
  }
}