@automattic/calypso-babel-config

Config

This package exports the configuration used for Calypso projects in ./babel.config.js. It is recommended to have your own babel.config.js in the root of the project and extend from this one. Example:

const { babelConfig } = require( '@automattic/calypso-babel-config' );
module.exports = babelConfig();

It supports a few configuration options:

isBrowser: boolean, whether the config is meant to be used in a Browser or in Node.js.
outputPOT: string, path to store the .POT files with the translations

Example (with default values):

const { babelConfig } = require( '@automattic/calypso-babel-config' );
module.exports = babelConfig( {
    isBrowser: true,
    outputPOT: './build',
} );

Presets

It exports three presets:

presets/default: default preset used in Calypso
presets/dependencies: used to transpile selected NPM dependencies from ESnext to the target's ES version.
presets/wordpress-element: used to transpile code for Wordpress

Example:

module.exports = {
    presets: [
        '@automattic/calypso-babel-config/presets/wordpress-element',
        '@automattic/calypso-babel-config/presets/default',
    ],
    plugins: [ 'my-custom-babel-plugin' ],
};

The default preset has a modules option that specifies whether we want to transpile ESM import and export statements. Most common values are false, which keeps these statements intact and results in ES modules as output, and 'commonjs', which transpiles the module to the CommonJS format. See the @babel/preset-env documentation for more details.

module.exports = {
    presets: [ [ '@automattic/calypso-babel-config/presets/default', { modules: 'commonjs' } ] ],
};

Another way to set the modules option is to set the MODULES environment variable to 'esm' (maps to false) or any other valid value. That's convenient for running Babel from command line, where specifying options for presets (--presets=...) is not supported.

The default preset also specifies corejs, debug, and useBuiltIns options that's passed through to @babel/preset-env.