JS utilities, extensible, dependency-free, to format and manipulate anything.

/**

Cut JS - https://cutjs.com

JS utilities, extensible, dependency-free, to format and manipulate anything.

Play with it here or in the TS Playground https://tsplay.dev/cutjs

*/

// Normal use
import { map } from "cutjs"
map({ a: 1 }, (v) => v - 1) //= {"a":0}

// Prototype use
import "cutjs?proto"
({ a: 1, b: 2 }).values().sum((v) => v - 1) //= 1

// Format a Date
new Date("2000").format("YYYY-QQ") //= "2000-Q1"
new Date("2000").format("day, month, year", "en") //= "January 1, 2000"
new Date("2000T00:00").format("long, short", "ja") //= "2000年1月1日 0:00"

// Format a String
"hello_world".format() //= "Hello World"
"hello_world".format("camel") //= "helloWorld"
"{}_{}".format(["hello", "world"]) //= "hello_world"

// Format a Number
0.30000000000000004.format() //= "0.3"
0.111.format("+0.##%") //= "+11.1%"
123456.789.format(2) //= "120k"
123456.789.format(".") //= "123,457"
123456.789.format("CN¥") //= "CN¥123,456.79"

// Parse a Date Expression
new Date("2000T00:00").parse("tomorrow") //= new Date("2000-01-02T00:00:00+01:00")
new Date("2000T00:00").parse("yesterday at 3pm") //= new Date("1999-12-31T15:00:00+01:00")
new Date("2000T00:00").parse("in one hour, two minutes and thirty-four seconds") //= new Date("2000-01-01T01:02:34+01:00")
new Date("2000T00:00").parse("6:30pm in three days") //= new Date("2000-01-04T18:30:00+01:00")

// Manipulate a Date
new Date("2000T00:00").plus("1 month").end("month").format("YYYY-MM-DD hh:mm") //= "2000-02-29 23:59"
new Date("2000T00:00").minus({ years: 1, months: 2 }).plus("1 year, 2 months").format("YYYY-MM-DD hh:mm") //= "2000-01-01 00:00"

// Manipulate an Object or Array
const users = [
  { name: "John", age: 30, city: "London" },
  { name: "Jane", age: 14, city: "New York" },
  { name: "Jean", age: 35, city: "Paris" },
]
const usersByCity = users.sort("-age").group("city") //~ {"Paris":[{"name":"Jean","age":35...}
const avgAgeByCity = usersByCity.map((g) => g.mean("age")) //~ {"Paris":35...}

// Manipulate a Function
function onEvent() {}
function expensiveFn() {}
const event = onEvent.throttle(1000).debounce(500)
const cache = expensiveFn.memoize()
const _fetch = fetch.decorate((fn, url, options) => {
  const timeout = options?.timeout || 5000
  const timer = new Promise((_, reject) => setTimeout(() => reject(new Error("Timeout")), timeout))
  return Promise.race([fn(url, options), timer])
})

Functions

• Generic: is, equal, access, transform
• Object: keys, values, entries, fromEntries, map, reduce, filter, find, findIndex
• Array: map, reduce, filter, find, findIndex, sort, group, unique, min, max, sum, mean, median
• Function: decorate, promisify, partial, memoize, every, wait, debounce, throttle
• String: words, format
• Number: duration, format
• Date: relative, getWeek, getQuarter, getLastDate, getTimezone, setTimezone, parse, format, modify, plus, minus, start, end
• RegExp: escape, replace, plus, minus

Development

bun install --no-save fast-check lodash-es @js-temporal/polyfill
bun test --watch --concurrent --coverage --only-failures
bunx prettier --write .

Principles

1. Shortcuts: Easy extension for input or error handling through decorators.

   // The "sort" function has a shortcut to handle different input types and convert them to the proper input
   const users = await fetch("https://jsonplaceholder.typicode.com/users")
   sort(users, "name") // accepts a string to sort by the property
   sort(users, "-address.city") // accepts a string with "-" to sort in descending order and "." to access nested properties
   sort(users, (v) => v.name) // accepts a function of length 1
   sort(users, ["-address.city", (v) => v.name]) // accepts an array for multi-sorting

2. Simplicity: Few core functions, easy to use and understand.

   // Object: map, reduce, filter, find (and other equivalent Array functions)
   // Array: sort, group, unique, min, max, sum, mean, median
   // String: format
   // Number: format
   // Date: format, parse, plus, minus, start, end

3. Union: Functions with the same name are combined into a single function that handles multiple types.

   // The "format" function is defined for String, Number, and Date
   format("hello world", "capitalize") //= "Hello world"
   format(123456.789, "$") //= "$123,456.79"
   format(new Date("2000"), "YYYY") //= "2000"

4. Powerful: Few core functions that cover most use cases, removing the need for additional libraries like lodash, date-fns, or numfmt.

Roadmap

• BLOG: Post / X / Hacker News / Product Hunt
• CODE: Typescript / TSDoc or JSDoc
• CODE: Versionning per function v1 2025-10 (1.2025.10), add tests per version
• DOC: comparison / benchmark with vanilla, lodash, date-fns, numfmt visible on the editor
• DOC: per function, from Markdown or TSDoc, like motion.dev or sugarjs.com
• PLAY: Button for Source Code + size / Gzip size
• PLAY: Collaboration / Multiplayer / CTRL-S to Share Link or Submit PR
• PLAY: AI Copilot
• PLAY: Monaco Editor or Github.dev like
• CODE: Additional Fn (forEach, findIndex, findLastIndex, some, every, flat, flatMap, reduceRight, concat, slice)
• EXPERIMENT: Iterator or AsyncIterator
• EXPERIMENT: Fuzzy tests
• EXPERIMENT: Security tests
• EXPERIMENT: LSP for test runner
• EXPERIMENT: Registry / Composition / Distribution with AI as a Shadcn or v0 registry

Inspiration

• utils lodash
• utils underscore
• utils sugar
• utils just
• utils core-js
• date date-fns
• date moment
• date dayjs
• date tempo
• d3
• jquery
• ixjs
• rxjs
• most
• ramda
• mathjs
• xstate
• motion
• microdiff
• numfmt
• sheetjs
• o-spreadsheet