Compatible Runners
Test Runners


Babel is the leading tool to compile EcmaScript 2015+ to EcmaScript 5, combined with ESLint to lint your code, you get the best preset to get started.


@swissquote/crafty-preset-babel is able to configure Babel with Webpack and rollup.js. This preset also supports Gulp but in this case it concatenates and minifies the files, it doesn't resolve imports.

Our Babel preset

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In @swissquote/crafty-preset-babel JavaScript is linted with ESLint, a powerful linter that supports plugins, our configuration follows the Swissquote JavaScript Guideline through our @swissquote/crafty-preset-eslint preset.

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npm install @swissquote/crafty-preset-babel --save
module.exports = {
  presets: [
    "@swissquote/crafty-runner-webpack", // optional
    "@swissquote/crafty-runner-gulp" // optional
  js: {
    app: {
      runner: "webpack", // Webpack, Gulp or rollup.js (optional if you have a single runner defined)
      source: "js/app.js"


With Webpack / rollup.js

Both runners have the same features in regards to Babel support. They will resolve your modules recursively and bundle them in one file or more if you do some code-splitting.

JavaScript External assets

By default, all bundlers include all external dependencies in the final bundle, this works fine for applications, but if you wish to build a multi-tenant application or a library, you don't wish to include all dependencies, because you'll end up with the same dependency duplicated.

The externals option allows you to define a list of libraries that are provided and should not be embedded in the build, here is an example :

module.exports = {
    // patterns are strings or globs
    externals: ["react", "react-dom", "squp", "squp/**"],
    js: {
        app: {
            // You can provide more items here, they will be merged with the main list for this bundle
            externals: ["my-plugin", "my-plugin/**"]

In this example react, react-dom and all modules starting with squp/ will be treated as external

You can see that globs were used here, note that they work for Webpack but rollup.js needs complete strings.

With Gulp

Gulp will not bundle your files like Webpack and rollup.js do, instead it will generate one output file per input file. This is useful if you are creating a library as it's the role of the final application to tree-shake what it doesn't need from your library.

Tree-shaking is powerful but is sub-optimal on big files as some code patterns are recognized as side-effects and thus aren't removed from your bundle even if they aren't used.

Usage with Jest

If you include both crafty-preset-babel and crafty-preset-jest. When running your tests with crafty test this preset will be use to convert all .js and .jsx files (source and test files)


Bundle options

Option Type Optional ? Runner Description
concat Boolean Yes Gulp This will merge all files together, outputting a single file. (This doesn't resolve imports, use Webpack or rollup.js for this)

Adding Babel plugins and presets

You can add, replace or remove plugins and add options to our default Babel configuration. To see which plugins are already included, you can go to the Swissquote Preset for Babel page.

module.exports = {
   * Represents the extension point for Babel configuration
   * @param {Crafty} crafty - The instance of Crafty.
   * @param {Object} bundle - The bundle that is being prepared for build (name, input, source, destination)
   * @param {Object} babelConfig - The current Babel configuration
  babel(crafty, bundle, babelConfig) {

After you did npm install --save-dev babel-plugin-transform-es5-property-mutators before, Babel will now use this plugin as well in each run.

This method is called once per bundle, so you can customize each bundle's configuration differently.