Overview

bitumen is a collection of utilities, types, and opinionated configuration for Babel, ESLint, Rollup, TypeScript, and Vitest.

Supported Environments

• Client side: Last two versions of Chrome, Edge, Firefox (+ ESR), and Safari
• Server side: Maintained versions of Node.js

Usage

Configuration

Babel

• Targets maintained versions of Node.js and the last two versions of Chrome, Edge, Firefox (+ ESR), and Safari;
• transpiles TypeScript to JavaScript and rewrites import extensions .?(c|m)ts?(x) → .?(c|m)js;
• preserves ECMAScript modules (i.e. no CommonJS conversion); and
• enables support for import attributes.

Option 1: 📍 package.json

{
  "babel": {
    "extends": "bitumen/configuration/babel"
  }
}

Option 2: 📍 babel.config.js

import base from 'bitumen/configuration/babel';

export default {
  ...base,
  // custom configuration and overrides
};

ESLint

Configuration for JavaScript, TypeScript, and optionally React, based on:

Plugin	Preset(s)
@eslint/js	recommended
@typescript-eslint	strict-type-checked, stylistic-type-checked
eslint-plugin-import-x	recommended, typescript
eslint-plugin-react	all
eslint-plugin-react-hooks	recommended

📍 .eslintrc.cjs

const base = require('bitumen/configuration/eslint');
const react = require('bitumen/configuration/eslint-react');

/** @type {import('eslint').Linter.Config} */
module.exports = {
  ...base,
  ...react,
  // custom configuration and overrides
};

Rollup

📍 rollup.config.js

import configure from 'bitumen/configuration/rollup';

import packageJson from './package.json';

export default configure(packageJson);

configure() returns a configuration object which:

• Reads entry points from package.json's exports field (no conditionals, null targets, or patterns).
• Writes distributable output to DIST_PATH, mirroring the directory structure of BUILD_PATH.
• Writes CommonJS modules to .cjs files and ES modules to .js files.
• Excludes test directories __mocks__, __tests__ from the output.
• Copies Sass stylesheets (.scss) from SRC_PATH to DIST_PATH.
• Copies TypeScript type declarations (.d.ts) from BUILD_PATH to DIST_PATH, giving them a .d.ts extension for ESM and a .d.cts extension for CommonJS.

The following environment variables must be set at runtime:

• BUILD_PATH: Where Babel and tsc output files can be found.
• DIST_PATH: Where Rollup is to write its distributable output.
• FORMAT: Type of modules to output; either 'es' (ESM) or 'cjs' (CommonJS).
• SRC_PATH: Where the original source code is located.

TypeScript

📍 tsconfig.json

{
  "extends": "bitumen/configuration/typescript",
  // custom configuration and overrides
}

Vitest

• Automatically clears mocks after each test,
• enables globals for automatic DOM clean-up between UI tests,
• looks for tests and mocks under ./src,
• requires 100% istanbul coverage,
• turns off watch mode by default, and
• uses thread workers for reduced overhead.

📍 vitest.config.js

import base from 'bitumen/configuration/vitest';

/** @type {import('vitest/config').UserConfig} */
export default {
  ...base,
  // custom configuration and overrides
};

Library

bitumen exposes named exports from the following entry points:

• collections
• configuration
• mixins
• types
• utils

For example, to implement SortedSet from collections:

import {SortedSet} from 'bitumen/collections';

const set = new SortedSet();

Type Declarations

For proper module and type resolution, set option compilerOptions.module to 'NodeNext' in jsconfig.json or tsconfig.json.

💡 bitumen's TypeScript configuration is already set up this way.