Client-side build tooling

Core JavaScript, CSS, and thirdparty dependencies are managed with the build tooling described below.

Note this only applies to core SilverStripe dependencies, you're free to manage dependencies in your project codebase however you like.


The NodeJS JavaScript runtime is the foundation of our client-side build tool chain. If you want to do things like upgrade dependencies, make changes to core JavaScript or SCSS files, you'll need Node installed on your dev environment. Our build tooling supports the v6.x (LTS) version of NodeJS. If you already have a newer version of Node.js installed, check out the Node Version Manager to run multiple versions in your environment.

Since we're compiling SVG icons, you'll also need to compile native Node addons, which requires gcc or a similar compiler - see node-gyp for instructions on how to get a compiler running on your platform.

yarn is the package manager we use for JavaScript dependencies. The configuration for an npm package goes in package.json. You'll need to install yarn after Node.js is installed. See yarn installation docs. We recommend using npm which comes with Node.js to install it globally.

npm install -g yarn

Once you've installed Node.js and yarn, run the following command once in each core module folders:


The Basics: ES6, Webpack and Babel

ECMAScript 6 (ES6) is the newest version of the ECMAScript standard. It has some great new features, but the browser support is still patchy, so we use Babel to transform ES6 source files back to ES5 files for distribution.

Webpack contains the build tooling to "transpile" various syntax patterns (ES6, SCSS) into a format the browser can understand, and resolve ES6's import (details). Webpack provides the entry point to our build tooling through a webpack.config.js file in the root folder of each core module.

Babel is a JavaScript compiler. It takes JavaScript files as input, performs some transformations, and outputs other JavaScript files. In SilverStripe we use Babel to transform our JavaScript in two ways.

Build Commands

The script property of a package.json file can be used to define command line scripts. A nice thing about running commands from an npm script is binaries located in node_modules/.bin/ are temporally added to your $PATH. This means we can use dependencies defined in package.json for things like compiling JavaScript and SCSS, and not require developers to install these tools globally. This means builds are much more consistent across development environments.

To run an npm script, open up your terminal, change to the directory where package.json is located, and run $ yarn run <SCRIPT_NAME>. Where <SCRIPT_NAME> is the name of the script you wish to run.


$ yarn run build

Runs Webpack to builds the core JavaScript files. You will need to run this script whenever you make changes to a JavaScript file.

Run this script with -- --watch to automatically rebuild on file changes. The first -- separator is required to separate arguments from NPM's own ones.

$ yarn run build -- --watch

For development only: Run this to keep webpack automatically rebuilding your file changes, this will also include *.map files for easier debugging. It is important to note that this should not be used for pushing up changes, and you should run yarn run build after you're done.

$ yarn run watch


$ yarn run css

Compiles all of the .scss files into minified .css files.

Run this script with -- --watch to automatically rebuild on file changes. The first -- separator is required to separate arguments from NPM's own ones.

$ yarn run css -- --watch


$ yarn run lint

Run linters (eslint and sass-lint) linters to enforce our JavaScript and CSS coding conventions.


$ yarn run test

Runs the JavaScript unit tests.


$ yarn run coverage

Generates a coverage report for the JavaScript unit tests. The report is generated in the coverage directory.

Requiring SilverStripe ES6 Modules in your own CMS customisation

SilverStripe creates bundles which contain many dependencies you might also want to use in your own CMS customisation (e.g. react). You might also need some of SilverStripe's own ES6 modules (e.g. components/FormBuilder).

To avoid double including these in your own generated bundles, we have exposed many libraries as Webpack externals. This helps to keep the file size of your own bundle small, and avoids execution issues with multiple versions of the same library.

In order to find out which libraries are exposed, check the framework/admin/client/src/bundles/ files for require('expose?...') statements.

A shortened webpack.config.js in your own module could look as follows:

module.exports = {
  entry: {
    'bundle': `mymodule/client/src/js/bundle.js`,
  output: {
    path: './client/dist',
    filename: 'js/[name].js',
  externals: {
    'components/FormBuilder/FormBuilder': 'FormBuilder',
    jQuery: 'jQuery',
    react: 'react',

Now you can use the following statements in your ES6 code without double includes:

import react from 'react';
import jQuery from 'jQuery';
import FormBuilder from 'components/FormBuilder/FormBuilder';

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