Assets provides a simple way to work with assets within Grind. It’s designed to get out of your way and allow you to work without worrying about running a watch command and waiting for files to compile. Once setup, all you need to do is store your assets in /resources/assets and the package will automatically detect changes and compile (and cache) on page load.

Assets comes with built in support for a bunch of asset types, but to maintain flexibility and minimize node_modules bloat, it doesn’t explicitly require any compiler depenencies. Instead you can pick and choose which you want to use, and install them directly.

Refer to the table below determine which dependencies you’ll need:

Compiler Install Command Description
Babel npm install --save-dev babelify browserify Provides support for using ES6/7 features in the browser
SCSS npm install --save-dev node-sass Provides SCSS compilation
Javascript npm install --save-dev uglify-js Provides JS minificaiton
CSS npm install --save-dev clean-css Provides CSS minification
SVG npm install --save-dev svgo Provides SVG optimization

Don’t worry if you forget to setup a dependency, Assets will let you know what to install if you try to use a compiler that doesn’t have it’s dependencies installed.

Most compilers match solely on file extension and don’t care where the file is located as long as it’s in /resources/assets.

Example: as long as the file is called main.scss, the SCSS compiler will compile regardless of whether it’s located at /resources/assets/scss/main.scss or /resources/assets/something-entirely-different/main.scss.

The exception to this rule is Babel. Since we want to minify vanilla JS files, the Babel compiler has an additional rule to ensure it doesn’t conflict with the JS minifier. All Babel files must be stored in a directory with “babel” in the path. For example both: /resources/assets/babel/main.js and /resources/assets/tooltip/babel/main.js will be compiled by Babel, however, /resources/assets/tooltip/main.js would not be.

Assets provides an assetPath() function that will look for your files in /resources/assets, so the file referenced in the snippet below should be in /resources/assets/scss/site.scss.

<link type="text/css" rel="stylesheet" href="{{ assetPath('scss/site.scss') }}" />

Assets also ships with a full asset container system to drop into views in a much cleaner way. It provides tags for asset, style, script, scss, babel and many more.

To use these tags, you must first configure your master layout to include them:

<!DOCTYPE html>
    {# …head… #}
    {% asset 'render', 'styles' %} {# <-- Renders included styles #}
    {# …body… #}
    {% asset 'render', 'scripts' %} {# <-- Renders included scripts #}

Once you’ve added those two lines to your master layout, you can begin using the view tags:

Assets supports the following style-related view tags:

  • style 'http://url' — will load any style path relative to /resources/assets or a fully qualified URL
  • css 'main' — will load /resources/assets/css/main.css
  • scss 'main' — will load /resources/assets/scss/main.scss
  • sass 'main' — will load /resources/assets/sass/main.sass

The following tags are also supported, but compilers are not yet built for them:

  • less 'main' — will load /resources/assets/less/main.less
  • styl 'main' — will load /resources/assets/styl/main.styl
  • stylus 'main' — will load /resources/assets/styl/main.stylus

Assets supports the following script-related view tags:

  • script 'http://url' — will load any script path relative to /resources/assets or a fully qualified URL
  • js 'main' — will load /resources/assets/js/main.js
  • babel 'main' — will load /resources/assets/babel/main.babel

The following tags are also supported, but compilers are not yet built for them:

  • coffee 'main' — will load /resources/assets/coffee/

Now that you know how the tags work, here’s an example of them in use:

{% extends 'layout/master.njk' %}
{% babel 'welcome' %}
{% scss 'welcome' %}
{% block content %}
  {# …some content… #}
{% endblock %}

When this view renders, it will load look something like this:

<!DOCTYPE html>
    <!-- …head… -->
    <link media="all" type="text/css" rel="stylesheet" href="http://localhost:3100/assets/scss/welcome.scss">
    <!-- …body… -->
    <script src="http://localhost:3100/assets/babel/app.js"></script> 

During your deploy process, you should run bin/cli assets:publish. This will precompile all assets and move them into the public/ directory.

As long as you’re using assetPath() or one of the asset container tags to reference your assets, they’ll start serving the compiled versions automatically.

Assets’ compilation system is fully extendable.

To write your own compiler, you must first extend the Compiler class from grind-assets and then implement the required methods:

import { Compiler } from 'grind-assets'
import PngCrusher from 'png-crusher'
import fs from 'fs-promise'
export class PngCompiler extends Compiler {
  // List of supported extensions 
  supportedExtensions = [ 'png' ]
  // The higher the value the more likely 
  // it is to be treated as a match, should 
  // two compilers want to match for the 
  // same asset 
  priority = 100
  compile(pathname, context) {
    if(!this.autoMinify) {
      return fs.readFile(pathname)
    return PngCrusher.crush(pathname)
  mime() { return 'image/png' }
  type() { return 'img' }
  extension() { return 'png' }

Now create a new AssetCompilersProvider to register the compiler:

import 'App/Assets/PngCompiler'
export function AssetCompilersProvider(app) {

The only other thing you need to is register your new AssetCompilersProvider in app/Bootstrap.js and your PNGs should start being crushed.

For more information on what Compilers can do, check out the existing compilers in Grind’s source code: