0.5.0 • Public • Published


Transfo offer both 'copy' and 'concat' task at once with the addition of streamed transformation of content and optional caching based on files mtime to limit unrequired file processing. Transfo should be used as an alternative to any grunt-contrib-copy and/or grunt-contrib-concat usage without any change in your grunt configuration (see compatibility test).


Functionalities overview

  • Replace grunt-contrib-copy without any configuration changes
  • Replace grunt-contrib-concat without any configuration changes
  • Lazy mode offer caching to reduce processing time if the source is not newer than the destination (see lazy option)
  • Use of Stream instead of buffering all the file content before copy or concat.
  • Pipe stream of sources and/or concatenated sources through a pipeline of Stream Transform (see transforms option).
  • Adding dynamically files to the processing queue while the sources goes through the transforms pipeline.
  • Processing more than one file at a time (see concurrency option)

Getting Started

This plugin requires Grunt ~0.4.1 and node >= 0.10.0

If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:

npm install grunt-transfo --save-dev

Once the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:


The "transfo" task


In your project's Gruntfile, add a section named transfo to the data object passed into grunt.initConfig().

You can use grunt-transfo in place of any grunt-contrib-copy or grunt-contrib-concat configuration.

  transfo: {
    options: {
      // Any grunt-contrib-copy and/or grunt-contrib-concat options
      // Any grunt-transfo options (see below)

    // Copy
    any_copy_task: {
      files: [
        {expand: true, src: ['path/**/*.js'], dest: 'build/', filter: 'isFile'}

    // Concat
    any_concat_task: {
      options: {
        stripBanners: true,
        banner: '/*! <%= %> - v<%= pkg.version %> - ' +
        '<%="yyyy-mm-dd") %> */',
      src: ['build/project.js','vendors/**/*.js'],
      dest: 'dist/built.js',
      expand: true



Type: Integer (>= 1) • Default: 1

How many files to proceed at the same time (copy and concat are asynchronously executed).


Type: Array of Function • Default: []

Each function is a constructor for a Transform stream. Any time a source is processed, each constructor is called with following arguments and must return a Transform stream.

Array of function(src, dest, options, addFiles) ...

  • src {String}: The source file path
  • dest {String}: The destination file path
  • options {Object}:
    • All your task options
    • isConcat {Boolean}: This is file will be concatenated with others
  • addFiles {Function}: A helper to add files to the process queue. Usefull to add file detected while the transformation (expl: assets in css source):
    • sources {Array|String}: One or many path to copy / concatenate
    • dest {String}: Destination path
    • options: Copy/concat options (transfo options)
options: {
  transforms: [
    // PassThrough ...
    function(src, dest, options, addFiles) { return new stream.Transform(); }

See too Stream Handbook to understand why using stream may be very powerfull.

See too through2 a nice wrapped around stream.Transform.


Type: Array of Function • Default: []

Like the transforms option but for the concatenated result.

Array of function(src, dest, options) ...

  • src {String}: The source file path
  • dest {String}: The destination file path
  • options {Object}:
    • All your task options
    • isConcat {Boolean}: This is file will be concatenated with others


Type: Boolean • Default: false

Do nothing if the destination file already exist with an equal or posterior mtime of the source(s). Both for copy and concat. Concat task a cached copy of the sources files after processing and transformation in tmp/grunt-transfo (see cache option below).

This option can be useful to reduce processing time. Especially when you use transfo with watch and livereload.


Type: String • Default: tmp/grunt-transfo

The path to use to store lazy & concatenation cached files. Remember to add this path to your clean task if you plan to use the lazy option.


Type: Boolean • Default: false

Only read source content through the process & transform pipeline but write nothing to the destination.

Any grunt-contrib-copy options

Any grunt-contrib-concat options

Usage Examples

The transfo-unifyurl library is an example of grunt-transfo stream transformation. transfo-unifyurl copy all css assets by adding them to the grunt-transfo pipeline.

npm install transfo-unifyurl
  transfo: {
    // This is a concat task. grunt-transfo allow copy task too
    concat_css: {
      src: ['src/**/*.css'],
      dest: 'build/css/compiled.css',
      options: {
        // Add unifyurl to the transformation pipeline
        transforms: [require('transfo-unifyurl')],
        // Set unifyurl options (below the default options):
        unifyurl: {
          // Assets destination: relative to the css destination path.
          dest:       './',

          // Url to the destination (default is a resolved
          // relative path based on dest value)
          url:        null,

          // List source extension to process. Other sources are ignored.
          extensions: ['.css']


In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using Grunt.

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  • jponchon