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A Grunt.js task that compiles CSS and JS files with respect of file modification date. For JS, it uses built-in UglifyJS minifier, for CSS — Yandex’s CSSO with automatic @import inlining and url() rewriting.

Unlike basic minifiers, this task generates a hidden catalog file (.build-catalog.json) that stores state, last compilation date and checksum of minified files. Every time you call frontend-* task, it will look into this catalog and check if the state of files being minified was changed. If not, the file will not be re-minified which saves CPU time and modification date. This date (or checksum hash) can be used to modify URLs to minified files for effective caching.


This plugin provides frontend-js, frontend-css and frontend-index multi-tasks. Global config can be defined in frontend key. All tasks are file-based. Here’s example Gruntfile.js:

module.exports = function(grunt) {
     // Global config for each frontend-* task. These values can 
     // be overridden in `options` key of each task 
     frontent: {
     // Force file minification even if they were not modified 
           force: false,
           // Path to project sources root folder. 
           // It is used to resolve absolute paths in CSS imports, 
           // for example: @import "/css/file.css" will be resolved  
           // to './src/files/css/file.css' 
           srcWebroot: './src/files',
           // Destination root folder. 
           // Used to update minified files paths in catalog, 
           // e.g. instead of storing '/Users/foo/project/out/css/minified.css' path,  
           // task will cut-out path to webroot and store '/css/minified.css' instead 
           webroot: './out',
           // A scheme for creating versioned URLs. Versioned URLs 
           // can are stored in catalog and used to rewrite paths  
           // for `url()` values of CSS. 
           // Can be a string or a function. 
           // A string is a template with the following placeholders: 
           // * version: version tag (in most cases it’s CRC32 of file) 
           // * url: absolute URL, e.g. `/path/to/file.css` 
           // * dirname: absolute path to file’s directory, e.g. `/path/to/` 
           // * basename: file’s full name, e.g. `file.css` 
           // * filename: name of file, e.g. `file` 
           // * ext: file’s extension, e.g. `css` 
           rewriteScheme: '/-/<%= version %><%= url %>',
           // function to post-process file’s content before it will be 
           // saved to disk 
           postProcess: function(content, fileInfo) {},
           // Directory to output .build-catalog.js and bundles 
           targetdir: '../vat/tmp',
           // Only process .build-catalog.js (no bundles) 
           onlyCatalog: true
     // Task for concatenating and minifying JS files 
        'frontend-js': {
            main: {
                // task options 
                options: {
                    // Minify JS 
                    minify: true,
                    // config for UglifyJS 
                    uglify: {}
                files: {
                    'out/js/f.js': [
        // Task for concatenating and minifying CSS files 
        'frontend-css': {
         main: {
             options: {
             // inline @imports 
             inline: true,
             // rewrite all url() to versioned ones. 
             // the `rewriteScheme` is used to create versioned URL 
             rewriteUrl: true,
             // minify CSS 
             minify: true
             files: [
                    {src: 'test/css/*.css', dest: 'out/css'}
        // Task fo indexing files and storing its’ version hash 
        // and verioned URL in catalog. Useful for fast lookups of  
        // versioned files 
        'frontend-index': {
         main: {
                files: [{src: 'test/css/**/*.{css,jpg,png}'}]

This task can be used together with docpad-plugin-frontend to automatically generate cache-effective URLs to assets for DocPad-generated web-site.