Example of a Minify Task using Jake

jake-minify.js

desc('Minify javascript.');
task('minify', function (params) {
    var task = this, startTime = +new Date(), minifiedCount = 0,
        targetPath = process.env.JS_BUILD_DIR || './';
        debugFiles = barkeep.fileListRecursive(path.join(BUILD_GLOBALS.output, targetPath), BUILD_GLOBALS.debugExpr),
        uglifyBin = path.join(__dirname, 'node_modules', 'uglify-js', 'bin', 'uglifyjs');
    console.log('Minifying javascript files...'.green);
    barkeep.directory(BUILD_GLOBALS.output); // Create build directory (if it doesn't exist).
    async.forEach(debugFiles, function (fileName, callback) {
        var extension = path.extname(fileName);
        var minFile = fileName.replace('.debug' + extension, '.min' + extension);    
        var cmd = util.format('%s %s > %s', uglifyBin, fileName, minFile);
        var child = exec(cmd, function (err) {
            if (err) {
                return callback(err);
            }
            callback(null);
        });    
    }, function (err) {
            console.log(util.format('  %s files minified.', debugFiles.length));
            console.log(util.format('  total time: %s ms', +new Date() - startTime));
            complete();    
    });
}, {async: true});