How to Minify CSS/JS Files (Using UglifyJS and UglifyCSS)

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Caution

Starting from Symfony 2.8, Assetic is no longer included by default in the Symfony Standard Edition. Refer to this article to learn how to install and enable Assetic in your Symfony application.

UglifyJS is a JavaScript parser/compressor/beautifier toolkit. It can be used to combine and minify JavaScript assets so that they require less HTTP requests and make your site load faster. UglifyCSS is a CSS compressor/beautifier that is very similar to UglifyJS.

In this article, the installation, configuration and usage of UglifyJS is shown in detail. UglifyCSS works pretty much the same way and is only talked about briefly.

Install UglifyJS

UglifyJS is available as a Node.js module. First, you need to install Node.js and then, decide the installation method: global or local.

Caution

Some Linux distributions rename the Node.js binary from node to nodejs. This may result in errors like "/usr/bin/env: node: No such file or directory". You can solve this problem with a symlink:

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$ ln -s /usr/bin/nodejs /usr/bin/node

Global Installation

The global installation method makes all your projects use the very same UglifyJS version, which simplifies its maintenance. Open your command console and execute the following command (you may need to run it as a root user):

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$ npm install -g uglify-js

Now you can execute the global uglifyjs command anywhere on your system:

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$ uglifyjs --help

Local Installation

It's also possible to install UglifyJS inside your project only, which is useful when your project requires a specific UglifyJS version. To do this, install it without the -g option and specify the path where to put the module:

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$ cd /path/to/your/symfony/project
$ npm install uglify-js --prefix app/Resources

It is recommended that you install UglifyJS in your app/Resources folder and add the node_modules folder to version control. Alternatively, you can create an npm package.json file and specify your dependencies there.

Now you can execute the uglifyjs command that lives in the node_modules directory:

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$ "./app/Resources/node_modules/.bin/uglifyjs" --help

Configure the uglifyjs2 Filter

Now we need to configure Symfony to use the uglifyjs2 filter when processing your JavaScripts:

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# app/config/config.yml
assetic:
    filters:
        uglifyjs2:
            # the path to the uglifyjs executable
            bin: /usr/local/bin/uglifyjs

Note

The path where UglifyJS is installed may vary depending on your system. To find out where npm stores the bin folder, execute the following command:

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$ npm bin -g

It should output a folder on your system, inside which you should find the UglifyJS executable.

If you installed UglifyJS locally, you can find the bin folder inside the node_modules folder. It's called .bin in this case.

You now have access to the uglifyjs2 filter in your application.

Configure the node Binary

Assetic tries to find the node binary automatically. If it cannot be found, you can configure its location using the node key:

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# app/config/config.yml
assetic:
    # the path to the node executable
    node: /usr/bin/nodejs
    filters:
        uglifyjs2:
            # the path to the uglifyjs executable
            bin: /usr/local/bin/uglifyjs

Minify your Assets

In order to apply UglifyJS on your assets, add the filter option in the asset tags of your templates to tell Assetic to use the uglifyjs2 filter:

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{% javascripts '@AppBundle/Resources/public/js/*' filter='uglifyjs2' %}
    <script src="{{ asset_url }}"></script>
{% endjavascripts %}

Note

The above example assumes that you have a bundle called AppBundle and your JavaScript files are in the Resources/public/js directory under your bundle. However, you can include your JavaScript files no matter where they are.

With the addition of the uglifyjs2 filter to the asset tags above, you should now see minified JavaScripts coming over the wire much faster.

Disable Minification in Debug Mode

Minified JavaScripts are very difficult to read, let alone debug. Because of this, Assetic lets you disable a certain filter when your application is in debug (e.g. app_dev.php) mode. You can do this by prefixing the filter name in your template with a question mark: ?. This tells Assetic to only apply this filter when debug mode is off (e.g. app.php):

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{% javascripts '@AppBundle/Resources/public/js/*' filter='?uglifyjs2' %}
    <script src="{{ asset_url }}"></script>
{% endjavascripts %}

To try this out, switch to your prod environment (app.php). But before you do, don't forget to clear your cache and dump your assetic assets.

Tip

Instead of adding the filters to the asset tags, you can also configure which filters to apply for each file in your application configuration file. See How to Apply an Assetic Filter to a specific File Extension for more details.

Install, Configure and Use UglifyCSS

The usage of UglifyCSS works the same way as UglifyJS. First, make sure the node package is installed:

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# global installation
$ npm install -g uglifycss

# local installation
$ cd /path/to/your/symfony/project
$ npm install uglifycss --prefix app/Resources

Next, add the configuration for this filter:

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# app/config/config.yml
assetic:
    filters:
        uglifycss:
            bin: /usr/local/bin/uglifycss

To use the filter for your CSS files, add the filter to the Assetic stylesheets helper:

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{% stylesheets 'bundles/App/css/*' filter='uglifycss' filter='cssrewrite' %}
    <link rel="stylesheet" href="{{ asset_url }}"/>
{% endstylesheets %}

Just like with the uglifyjs2 filter, if you prefix the filter name with ? (i.e. ?uglifycss), the minification will only happen when you're not in debug mode.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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