Using Jest and ESlint with babel


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If you are using jest to test your project, and ESLint for linting then you might want to add a babel.config.js file for uniform babel rules.

Using Same rule without customization

By default, @wpackio/scripts ignores any babel.config.js and .babelrc files. So even if you do put such files in your project root, those will be picked up by Jest or ESLint, but not by @wpackio/scripts. In small use cases, this is perhaps the intended feature. In this case, create a babel.config.js file in the root of your project and put the following code.


import {
} from '@wpackio/scripts';

module.exports = api => {
	// create cache based on NODE_ENV
	api.cache.using(() => process.env.NODE_ENV);

	// make use of some configuration
	const isDev = api.env('development');
	const isTest = api.env('test');
	const hasReact = true;

	const presetOptions = getDefaultBabelPresetOptions(hasReact, isDev);

	// If test, then change modules and targets
	// since jest works in node and understands only cjs modules
	if (isTest) {
		presetOptions.presetEnv.targets = {
			node: 'current',
		presetOptions.presetEnv.modules = 'commonjs';

	// Now get the presets and create babel config
	// assuming we are using typescript
	// otherwise don't pass anything to the second parameter of getBabelPresets
	// or pass 'flow` for flowtype
	const babelConfig = {
		presets: getBabelPresets(presetOptions, 'typescript'),

	// return it
	return babelConfig;

The above will create same babel rule for jest and eslint as used internally by @wpackio/scripts.

Override @wpackio/scripts rules

If you want to completely remove any babel rule set by @wpackio/scripts and would only want to use one single babel.config.js instead, do the followings.

Instruct @wpackio/scripts to not pass any rule to babel-loader

Edit your wpackio.project.js file and put

module.exports = {
	// config
	// this tells wpackio-scripts to use your own babel.config.js file
	useBabelConfig: true,

Now this will remove all rules from babel-loader for both javascript and typescript files. So it will pick your own babel.config.js file.

Now go ahead and write your custom babel.config.js file making sure it matches your project requirements. From now on, all tools including Jest, ESLint and @wpackio/scripts will follow the same config.

For more information, do read the custom babel configuration tutorial.

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