A simple build tool with a fluent interface

Jager Jager on NPM

A simple build tool with a fluent interface


var jager = require('jager');

// create a new chain of actions
var livereload = jager.create()
    ('livereload'); // add a plugin to the chain

// create a chain which handles the javascript processing
var js = jager.create()
    ('src', 'jagerfile.js') // source of the chain
    ('uglify') // chain it to the uglify plugin
    ('rename', 'renamed-jagerfile.js') //  rename the file
    ('dest', '.'); // write the file

// create tasks to execute the defined chains
jager.task('js', js);

// `{ watch: true }` is used to tell jager to rerun the task when
// any of the source files or its dependencies change
jager.task('watch:js', { watch: true },  js, livereload);

// create a chain to process the less files
var less = jager.create()
    ('src', 'main.less', { dependencies: '*.less' }) // specify a source file and a list of possible dependencies
    ('less') // chain it to the less plugin
    ('rename', 'main.css') // rename it
    ('autoprefixer') // call the autoprefixer plugin on it
    ('dest', '.'); // write the file

// create tasks for the less chains
jager.task('less', less);
jager.task('watch:less', { watch: true }, less, livereload);

// create a task for two chains, which will run simultaneously
jager.task('watch', { watch: true }, [js, less], livereload);


Install with npm install --save jagerand npm install -g jager, after create a Jagerfile.jsfile (see example above) in your project root. Then you can run jager [task]to execute your task.

Alternatively you can skip the global install and use the version in node_modules/.bin/, which is automatically added to your PATHwhen you run it with npm run. For example, the following package.jsonscript would run the watch task without the globally installed version.

    "scripts": {
        "watch": "jager watch"

Run with npm run watch, no need for the global!

Create a plugin

Plugins have pretty simple structure, like so:

module.exports = function(options) {
    // the arguments to this function come from the `Jagerfile.js` file, for example:
    // `('src', 'script.js')` would give the `'script.js'` as argument

    return function(files, cb) {
        // files contains an array with `jager.File` instances, which you can manipulate
        cb(null, files);

Jager automatically loads plugins when they follow the convention that when the module name is jager-something-something, it will load that plugin whenn you call it with ('something-something'). You can also just pass the function you normally return in your plugin directly to Jager:

    (function(files, cb) {
        cb(null, files);


  • filename(): Return the filename for the file
  • contents([string]): When an argument is given, the contents are updated. Returns the contents
  • buffer([buffer])): When an argument is given, the internal buffer is updated. Return the internal buffer
  • stat([stat]): When an argument is given, the stat is updated. Return the stat
  • rename(filename): Rename the file, the stat is updated to now

You can use both contents()and buffer()mixed, they will be converted on the fly when needed.

Built-in plugins

Jager has some builtin plugins to get you started:

src: Add source files

Add files to the chain used for processing

API: ('src', pattern[, options])

  • pattern: a glob to find files
  • options:
    • dependencies: a glob to describe dependencies of this source, is used to trigger the rerun when a file is changed (default: null)

dest: Write files

Write files in the chain to a given destination. By default only files with a newer mtimeare written.

API: ('dest', dir[, options])

  • dir: the directory to which the files in the chain are written, if the directory does not exist, it's created
  • options:
    • checkContents: Check for the contents of the new file location, if the contents is the same, the file is not written (default: false)

browserify: Process a file with browserify

Browserify lets you require('modules')in the browser by bundling up all of your dependencies. When watch mode is active watchifyis used to produces faster builds.

API: ('browserify'[, options])

  • options:
    • See the browserify optionsfor details
    • Extra options:
      • babel: When set the babel transform is used, see babel optionsfor more options
      • sourceMap: These options are in line with the options used in the less options(currently only sourceMapBasepathis supported)

newer: Filter old files out of the chain

API: ('newer', target[, options])

  • target: The target to which you want to compare the files in the chain
  • options:
    • basePath: Common base path between target and source files (default: cwd)
    • checkContents: Check for the contents of the new file location, if the contents is the same, the file is filteredwritten (default: false)

uglify: Uglify javascript

Compress javascript files

API: ('uglify')

concat: Combine source files

Combine all files in the chain into a new file

API: ('concat', filename)

  • filename: The filename for the new file

rename: Rename a file

Rename the first file in the chain, if it doesn't exist, an empty file is added to the chain

API: ('rename', filename)

  • filename: the new filename. The following replacements will be done in the filename:
    • [timestamp]: the current timestamp is included
    • [hash]: the md5 checksum of the contents is included

less: Process less files

Process less file into css files

API: ('less'[, options])

autoprefixer: Add vendor prefixes to css

Plugin to parse CSS and add vendor prefixes to CSS rules using values from Can I Use. It is recommendedby Google and used in Twitter, and Taobao.

API: ('autoprefixer'[, browserVersions])

angular-templates: Create cache file for all angular templates

Instead of loading all template files through ajax, include this cache file to make the lookup to these template files instant

API: ('angular-templates'[, options])

  • options:
    • base: Use this to cut a part from the filenames in the cache file, to make it correspond with your template definitions (default: '')
    • filename: filename of the output file (default: templates.js)

ngmin: Create a version of angular-js-file that is uglify save

Create an properly annotated version of a angular file with ngmin.

API: ('ngmin')

bower-src: Add files from your bower config

Recursively add the main files from your bower config to your chain.

API: ('bower', pattern)

  • pattern: glob to match the wanted bower package, ex: 'jquery'would add the main file for jquery

babel: Transform ES6 to ES5 javascript

Babel will turn your ES6+ code into ES5 friendly code, so you can start using it right now without waiting for browser support.

API: ('babel'[, options])

livereload: Reloads your browser when files change

Notify the browser of any changes in your chain, compatible with at least the Chrome pluginand Firefox plugin.

API: ('livereload'[, options])

  • options:
    • port: port used by the livereload server (default: 35729)

imagemin: Minify images seamlessly

Minifies all images (based on extension) in the chain with imagemin.

API: ('imagemin'[, options])

postcss: Transforming CSS with JS plugins

PostCSSis a tool for transforming CSS with JS plugins. These plugins can support variables and mixins, transpile future CSS syntax, inline images, and more.

API: ('postcss'[, options])

extract-sourcemap: Extract sourcemaps into separate files

API: ('extract-sourcemap')

Creates a file in the same directory as the input file, with a .mapsuffix. The sourcemap in the file is replace with a comment referencing the new file.

modernizr: Create on the fly modernizr builds

API: ('modernizr'[, options])

clean-css: Library for minifying CSS files

Clean-css is a fast and efficient Node.js library for minifying CSS files. According to testsit is one of the best available.

API: ('clean-css'[, options])




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