JS utilities, extensible, dependency-free, to format and manipulate anything.
/**Cut JS - https://cutjs.comJS utilities, extensible, dependency-free, to format and manipulate anything.Play with it here or in the TS Playground https://tsplay.dev/cutjs*/// Normal useimport{map}from"cutjs"map({a: 1},(v)=>v-1)//= {"a":0}// Prototype useimport"cutjs?proto"({a: 1,b: 2}).values().sum((v)=>v-1)//= 1// Format a DatenewDate("2000").format("YYYY-QQ")//= "2000-Q1"newDate("2000").format("day, month, year","en")//= "January 1, 2000"newDate("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 Number0.30000000000000004.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 ExpressionnewDate("2000T00:00").parse("tomorrow")//= new Date("2000-01-02T00:00:00+01:00")newDate("2000T00:00").parse("yesterday at 3pm")//= new Date("1999-12-31T15:00:00+01:00")newDate("2000T00:00").parse("in one hour, two minutes and thirty-four seconds")//= new Date("2000-01-01T01:02:34+01:00")newDate("2000T00:00").parse("6:30pm in three days")//= new Date("2000-01-04T18:30:00+01:00")// Manipulate a DatenewDate("2000T00:00").plus("1 month").end("month").format("YYYY-MM-DD hh:mm")//= "2000-02-29 23:59"newDate("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 Arrayconstusers=[{name: "John",age: 30,city: "London"},{name: "Jane",age: 14,city: "New York"},{name: "Jean",age: 35,city: "Paris"},]constusersByCity=users.sort("-age").group("city")//~ {"Paris":[{"name":"Jean","age":35...}constavgAgeByCity=usersByCity.map((g)=>g.mean("age"))//~ {"Paris":35...}// Manipulate a FunctionfunctiononEvent(){}functionexpensiveFn(){}constevent=onEvent.throttle(1000).debounce(500)constcache=expensiveFn.memoize()const_fetch=fetch.decorate((fn,url,options)=>{consttimeout=options?.timeout||5000consttimer=newPromise((_,reject)=>setTimeout(()=>reject(newError("Timeout")),timeout))returnPromise.race([fn(url,options),timer])})- 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
bun install --no-save fast-check lodash-es @js-temporal/polyfill
bun test --watch --concurrent --coverage --only-failures
bunx prettier --write .# For AI Agents:
RUNS=10000 TZ="Europe/Paris" bun test --concurrent --only-failures- 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 inputconstusers=awaitfetch("https://jsonplaceholder.typicode.com/users")sort(users,"name")// accepts a string to sort by the propertysort(users,"-address.city")// accepts a string with "-" to sort in descending order and "." to access nested propertiessort(users,(v)=>v.name)// accepts a function of length 1sort(users,["-address.city",(v)=>v.name])// accepts an array for multi-sorting
- 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
- 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 Dateformat("hello world","capitalize")//= "Hello world"format(123456.789,"$")//= "$123,456.79"format(newDate("2000"),"YYYY")//= "2000"
- Powerful: Few core functions that cover most use cases, removing the need for additional libraries like lodash, date-fns, or numfmt.
- 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