# Managing CSS and JavaScript in Chamilo.
The folder "assets" will be processed by the js library Webpack Encore and the result will be saved in public/build folder.
For this, we first need to install yarn.
Yarn is a JavaScript dependencies manager similar to Bower (that we also used for development in Chamilo 1.11.x),
only that Bower is deprecated now.
To install yarn, follow the installation instructions here https://yarnpkg.com/en/docs/install
After the installation run this command in the Chamilo root:
``yarn install``
yarn will read the dependencies in the **packages.json** file and save the dependencies in the 'node_modules' folder (which must **NOT** be committed** to the Chamilo repository).
# Configuring Encore/Webpack
Webpack takes CSS, JS and other files and generates tidy single-files to attach to your web package.
The behaviour of how packages will be processed is describe here: "webpack.config.js".
If the public/js/fos_js_routes.json file does not exist (or if you're in doubt about the version of your PHP libs), run:
```
composer update
bin/console fos:js-routing:dump --format=json --target=public/js/fos_js_routes.json
```
Then, to create the public/build contents, run one of the following commands:
To compile assets just once:
``yarn run encore dev``
To compile assets and minify & optimize them:
``yarn run encore production``
For more detail information please visit:
https://symfony.com/doc/current/frontend.html
