@mrmartineau/kit

A personal collection of utilities, components, and hooks for use across projects.

1 Feb 2026

npmx.dev Repo TypeScript, Biome, OxLint, OxFmt, ESLint, Prettier

A monorepo of personal utilities, components, and hooks extracted from real projects. Provides consistent, well-tested building blocks for use across different TypeScript codebases.

Project README

@mrmartineau/kit

A personal collection of sounds, utilities, components, and hooks for use across projects.

Installation

bun add @mrmartineau/kit

This package provides configuration files and static assets only, with no runtime dependencies — it does not install the underlying tools. Install whichever tools you actually need in your project:

# Biome (linter + formatter)
bun add -d @biomejs/biome

# oxc (linter + formatter)
bun add -d oxlint oxfmt

# ESLint + Prettier
bun add -d eslint @eslint/js prettier

# Prettier with .astro support
bun add -d prettier prettier-plugin-astro

You don't need all of them — just pick the tools you want to use and reference the matching config from this package.

Project structure

src/
├── biome/        # Shared Biome config
├── eslint/       # Shared ESLint flat config
├── oxfmt/        # Shared oxfmt config
├── oxlint/       # Shared oxlint config
├── prettier/     # Shared Prettier config
├── sounds/       # Static audio assets (.mp3) — not bundled
├── utils/        # Utility functions
├── components/   # Reusable components
├── hooks/        # Reusable hooks
└── scripts/      # Standalone scripts

Usage

Sounds

Sound files are exposed as raw .mp3 files via subpath exports — they are not bundled or transformed. Your bundler or runtime resolves them as static assets.

Import a sound file directly:

// Resolves to the raw .mp3 file in node_modules
import clickSound from '@mrmartineau/kit/sounds/click_001.mp3'

// Use with Audio API
const audio = new Audio(clickSound)
audio.play()

Use the metadata module for programmatic access:

import {
  sounds,
  soundCategories,
  getSoundsByCategory,
  getSoundPath,
} from '@mrmartineau/kit/sounds'

// List all sound names
console.log(sounds)

// Get all sounds in a category
const clickSounds = getSoundsByCategory('click')
// => ["click_001", "click_002", "click_003", "click_004", "click_005"]

Available sound categories: back, bite, bong, boop, buy, click, close, confirmation, disable, drop, enable, error, glass, glitch, maximize, menu, minimize, open, pluck, plunger, pop, question, rising, scratch, scroll, select, switch, tick, toggle

Biome

Shared Biome config for linting and formatting. Biome natively supports extending from packages via its extends field.

In your project's biome.json:

{
  "$schema": "https://biomejs.dev/schemas/2.5.7/schema.json",
  "extends": ["./node_modules/@mrmartineau/kit/src/biome/biome.json"]
}

Included settings: space indentation (2), single quotes, no semicolons, trailing commas, 100 line width, import sorting, recommended lint rules, React domain rules.

The config is marked "root": false so Biome doesn't mistake it for a second root configuration when it sits inside a project. root is not inherited through extends, so your own biome.json stays the root.

Object-key sorting (assist.actions.source.useSortedKeys) is deliberately not enabled — it rewrites object literals in your source on save, which is surprising and occasionally meaningful. Turn it on per-project if you want it.

oxlint

Shared oxlint config. Reference it via extends in your .oxlintrc.json:

{
  "$schema": "https://raw.githubusercontent.com/oxc-project/oxc/main/npm/oxlint/configuration_schema.json",
  "extends": ["./node_modules/@mrmartineau/kit/src/oxlint/.oxlintrc.json"]
}

Included settings: correctness (error), suspicious + perf (warn), browser + node + es2024 envs, typescript/unicorn/import/react/jsx-a11y plugins, no-console warn, no-debugger error, typescript/consistent-type-imports error.

consistent-type-imports pairs with the verbatimModuleSyntax TypeScript setting this kit also uses: without it, a type-only import that's missing the type keyword survives into the emitted JavaScript as a real runtime import.

oxfmt

Shared oxfmt config. Reference it when running oxfmt:

oxfmt -c ./node_modules/@mrmartineau/kit/src/oxfmt/.oxfmtrc.json

Or copy the settings into your own .oxfmtrc.json. The settings are kept consistent with the Biome config: single quotes, no semicolons, 2-space indentation, 100 print width.

ESLint

Shared ESLint flat config with a small set of base rules. It carries no formatting rules — use Prettier, Biome or oxfmt for that.

This config layers on top of a recommended base rather than replacing it, so that this package stays dependency-free. Compose it with @eslint/js yourself — on its own it will not give you no-unused-vars, no-undef and friends:

import js from '@eslint/js'
import kit from '@mrmartineau/kit/eslint'
import { defineConfig } from 'eslint/config'

export default defineConfig([
  js.configs.recommended,
  {
    files: ['**/*.{ts,tsx,js,jsx}'],
    extends: [...kit],
  },
])

Included rules: prefer-const, no-var, no-console (warn), no-debugger (error), no-alert (warn), eqeqeq, object-shorthand, prefer-template, prefer-arrow-callback and curly (multi-line). Add your own TypeScript/React plugins on top.

curly is the one stylistic-looking rule here, and it's deliberate: it guards against a statement being accidentally added outside an unbraced block, which no formatter will catch for you.

Opt-in: ban `../` imports

no-restricted-imports is exported separately rather than being on by default — it only makes sense once a project has path aliases configured, and colocated tests or sibling-directory imports in a library layout can't satisfy it at all.

import kit, { noRelativeParentImports } from '@mrmartineau/kit/eslint'

export default defineConfig([...kit, noRelativeParentImports])

Prettier

Shared Prettier config. Reference it in your package.json:

{
  "prettier": "@mrmartineau/kit/prettier"
}

Or create a .prettierrc.json:

"@mrmartineau/kit/prettier"

Included settings: single quotes, no semicolons, 2-space indentation, trailing commas, 100 print width.

Astro

Prettier can't parse .astro files on its own, so there's a separate config that layers prettier-plugin-astro on top of the base one. It's kept separate because Prettier hard-errors when a plugin listed in plugins can't be resolved — putting the plugin in the base config would break every non-Astro consumer.

bun add -d prettier prettier-plugin-astro

In your package.json:

{
  "prettier": "@mrmartineau/kit/prettier/astro"
}

Or in a prettier.config.mjs:

export { default } from '@mrmartineau/kit/prettier/astro'

Everything from the base config still applies — the .astro frontmatter and expressions are formatted with the same single quotes, no semicolons, 2-space indentation and 100 print width.

If you also use prettier-plugin-tailwindcss, it must come last in plugins, so extend the config rather than referencing it directly:

import astro from '@mrmartineau/kit/prettier/astro'

export default {
  ...astro,
  plugins: [...astro.plugins, 'prettier-plugin-tailwindcss'],
}

Biome and oxfmt do not format .astro files — Prettier is the only option in this kit for an Astro project's templates.

Utils, Components, Hooks

import { ... } from "@mrmartineau/kit/utils";
import { ... } from "@mrmartineau/kit/components";
import { ... } from "@mrmartineau/kit/hooks";

Formatters

A collection of number and string formatters. All number formatters wrap Intl.NumberFormat and default to the en-GB locale.

import {
  formatNumberAccounting,
  formatNumberBase,
  formatNumberBytes,
  formatNumberCompact,
  formatNumberCurrency,
  formatNumberDecimal,
  formatNumberDecimalForceDecimalPlaces,
  formatNumberOrdinal,
  formatNumberPercent,
  formatNumberRange,
  formatNumberSignDisplay,
  formatInitials,
  formatList,
  maskString,
  normalizeWhitespace,
  pluralize,
  slugify,
  stripDiacritics,
  toCamelCase,
  toKebabCase,
  toPascalCase,
  toSnakeCase,
  toStartCase,
  truncate,
} from '@mrmartineau/kit/utils'

Number formatters

Function	Signature	Example
`formatNumberBase`	`(value, options?)`	`formatNumberBase(1234)` → `"1,234"`
`formatNumberDecimal`	`(value, decimalCount = 2, options?)`	`formatNumberDecimal(1234.567, 2)` → `"1,234.57"`
`formatNumberDecimalForceDecimalPlaces`	`(value, decimalCount = 2, options?)`	`formatNumberDecimalForceDecimalPlaces(10, 2)` → `"10.00"`
`formatNumberCurrency`	`(value, currency, decimalCount = 2, options?)`	`formatNumberCurrency(1234, "GBP")` → `"£1,234.00"`
`formatNumberAccounting`	`(value, currency, decimalCount = 2, options?)` — negatives wrapped in parens	`formatNumberAccounting(-100, "USD")` → `"($100.00)"`
`formatNumberPercent`	`(value, decimalCount = 2, options?)` — value already in decimal form (`0.42` → `42%`)	`formatNumberPercent(0.421)` → `"42.1%"`
`formatNumberCompact`	`(value, display = "short", options?)`	`formatNumberCompact(1200)` → `"1.2K"`
`formatNumberOrdinal`	`(value, locale = "en-GB")`	`formatNumberOrdinal(3)` → `"3rd"`
`formatNumberBytes`	`(bytes, binary = false, decimalCount = 2)`	`formatNumberBytes(1536, true)` → `"1.5 KiB"`
`formatNumberRange`	`(min, max, options?, locale = "en-GB")`	`formatNumberRange(1, 5)` → `"1–5"`
`formatNumberSignDisplay`	`(value, decimalCount = 2, signDisplay = "exceptZero", options?)`	`formatNumberSignDisplay(5)` → `"+5"`

String formatters

Function	Signature	Example
`formatList`	`(array, options?)` — wraps `Intl.ListFormat`	`formatList(["a","b","c"])` → `"a, b, and c"`
`toStartCase`	`(str)`	`toStartCase("hello_world")` → `"Hello World"`
`toCamelCase`	`(str)`	`toCamelCase("hello_world")` → `"helloWorld"`
`toPascalCase`	`(str)`	`toPascalCase("hello_world")` → `"HelloWorld"`
`toKebabCase`	`(str)`	`toKebabCase("helloWorld")` → `"hello-world"`
`toSnakeCase`	`(str)`	`toSnakeCase("helloWorld")` → `"hello_world"`
`truncate`	`(str, maxLength, { ellipsis = "…", wordBoundary = false }?)`	`truncate("Hello world", 8)` → `"Hello w…"`
`slugify`	`(str)`	`slugify("Hello, World!")` → `"hello-world"`
`pluralize`	`(count, singular, plural?)`	`pluralize(2, "child", "children")` → `"children"`
`stripDiacritics`	`(str)`	`stripDiacritics("café")` → `"cafe"`
`normalizeWhitespace`	`(str)`	`normalizeWhitespace(" a\n\tb ")` → `"a b"`
`maskString`	`(str, { visibleStart = 0, visibleEnd = 4, maskChar = "•" }?)`	`maskString("4242424242424242")` → `"••••••••••••4242"`
`formatInitials`	`(name, maxLength = 2)`	`formatInitials("John Smith")` → `"JS"`

Type checks

Runtime "is this a…?" checks. Each one is a TypeScript type guard, so the value's type narrows after the check. Use them on data you don't control: API responses, JSON.parse, localStorage, catch errors.

import { isDefined, isPlainObject, isString } from '@mrmartineau/kit/utils'

const ids = [1, null, 2].filter(isDefined) // number[]

Function	`true` for
`isString`	strings
`isBoolean`	booleans
`isBigInt`	bigints
`isSymbol`	symbols
`isFunction`	functions, including classes
`isPrimitive`	anything that isn't an object or function, including `null`
`isNumber`	any number, including `NaN` and `Infinity`
`isFiniteNumber`	numbers that aren't `NaN` or `Infinity`
`isInteger`	whole numbers
`isNumericString`	strings that hold a finite number: `'42'` yes, `''` and `'12px'` no
`isNull`	`null`
`isUndefined`	`undefined`
`isNil`	`null` or `undefined`
`isDefined`	anything but `null` or `undefined`; works as a `filter` callback
`isObjectLike`	any non-null object, arrays included
`isObject`	non-null objects that aren't arrays
`isPlainObject`	`{}` literals and `Object.create(null)` only
`hasKey`	objects with that key as their own property: `hasKey(data, 'id')`
`isArray`	arrays
`isArrayOf`	arrays where every item passes a check: `isArrayOf(value, isString)`
`isValidDate`	`Date`s that hold a real date, not `new Date('nonsense')`
`isRegExp`	regular expressions
`isMap`	`Map`s
`isSet`	`Set`s
`isError`	`Error`s and subclasses
`isPromiseLike`	promises and anything else with a `.then` method
`isIterable`	anything `for...of` can loop over, strings included
`isEmpty`	`null`, `undefined`, `''`, `[]`, `{}` and empty `Map`s and `Set`s

More detail and the reasoning behind each one: Type check helpers.

Exports map

Specifier	Resolves to
`@mrmartineau/kit`	`src/index.ts`
`@mrmartineau/kit/biome`	`src/biome/biome.json`
`@mrmartineau/kit/eslint`	`src/eslint/index.ts`
`@mrmartineau/kit/oxlint`	`src/oxlint/.oxlintrc.json`
`@mrmartineau/kit/oxfmt`	`src/oxfmt/.oxfmtrc.json`
`@mrmartineau/kit/prettier`	`src/prettier/.prettierrc.json`
`@mrmartineau/kit/prettier/astro`	`src/prettier/astro.js`
`@mrmartineau/kit/sounds`	`src/sounds/index.ts` (metadata)
`@mrmartineau/kit/sounds/*.mp3`	`src/sounds/*.mp3` (raw files)
`@mrmartineau/kit/utils`	`src/utils/index.ts`
`@mrmartineau/kit/components`	`src/components/index.ts`
`@mrmartineau/kit/hooks`	`src/hooks/index.ts`

Development

This repo dogfoods its own Biome config — the root biome.json extends src/biome/biome.json, so a change to the shared config shows up here first.

bun run lint       # check
bun run lint:fix   # check and apply fixes
bun run format     # format only
bun test
bun run typecheck

CI runs biome ci . alongside typecheck and tests on every pull request.

Attribution

Sounds

Sounds by Kenney, licensed under CC0 1.0 and some from use-sound by Josh Comeau

@mrmartineau/kit

Installation

Project structure

Usage

Sounds

Biome

oxlint

oxfmt

ESLint

Opt-in: ban ../ imports

Prettier

Astro

Utils, Components, Hooks

Formatters

Number formatters

String formatters

Type checks

Exports map

Development

Attribution

Sounds

Opt-in: ban `../` imports