All Functions

All Functions

464 implemented helpers + 60 covered by native JavaScript APIs, sorted alphabetically.

Function	Category	Description
AbortSignalLike	type	What helpers4 needs of an `AbortSignal`: whether it is aborted, why, and a way to listen for the abort.
add / subtract (date arithmetic)	date	native JS Temporal.PlainDate.prototype.add(duration) / .subtract(duration) (Temporal (Stage 3))
addDays	date	Adds days to a date.
addMonths	date	Adds months to a date.
addYears	date	Adds years to a date.
agree	license	Whether two raw license strings agree closely enough to count as “no real conflict” — true when their family sets share…
AlpineDependency	package	One package reference of an Alpine (apk) `depends` list.
AlpineOperator	package	The operators of an Alpine (apk) version constraint, as apk writes them: the five comparisons;
analyzeCommits	commit	Analyses a list of commits to suggest a semantic version bump.
applyToPoint	geometry	Transforms a point by a matrix.
applyToRect	geometry	Transforms a rectangle by a matrix and returns its bounding box: the smallest axis-aligned rectangle that contains it.
ArchDependency	package	One package reference of an Arch Linux `depends` array.
argbToRgb	color	Converts a 32-bit packed ARGB integer (as used by e.g.
blendColors	color	Composites a source color over a backdrop with a blend mode, as the browser does for `mix-blend-mode` (W3C Compositing…
Brand	type	Brands a base type `T` with a phantom tag `B` to create a nominal type.
buildConventionalCommitRegex	commit	Builds a regular expression matching the **subject line** of a Conventional Commits message.
buildStatusTable	ci	Builds a Markdown table body from a map of job names to CI/CD statuses.
camelCase	string	Converts a string to camelCase.
camelCaseKeys	object	Recursively transforms every key of a plain object (including keys nested inside arrays and nested objects) to camelCas…
capitalize	string	Capitalizes the first letter of a string.
cartesianProduct	array	Computes the Cartesian product of the provided arrays.
ceil / floor	number	native JS Math.ceil() / Math.floor() (ES1)
chunk	array	Chunks an array into smaller arrays of specified size.
clamp	number	Clamps a number between min and max values
clampDate	date	Clamps a date to a [min, max] range.
cleanPath	url	Clean an URL by removing duplicate slashes.
clone	object	Creates a shallow copy of a value — one level deep, unlike cloneDeep.
cloneDeep	object	Creates a deep copy of an object or array.
combine	observable	Combine two observables with a map function and an optional pre-treatment.
combineLatest	observable	Combines multiple Observables to create an Observable whose values are calculated from the latest values of each of its…
combineSortFns	array	Chains multiple sort functions into a single comparator: the first function decides the order unless it reports a tie (…
compact	array	Removes all falsy values (`false`, `null`, `undefined`, `0`, `""`, `NaN`) from an array.
compact	object	Removes all entries with falsy values (`false`, `null`, `undefined`, `0`, `""`, `NaN`) from an object.
compare	date	Comparison of two dates.
compare	version	Compares two version strings, according to the given `scheme`.
compare (ordering)	date	native JS Temporal.PlainDate.compare(a, b) / Temporal.Instant.compare(a, b) (Temporal (Stage 3))
ComparisonOperator	package	The operators of an RPM or Arch Linux version constraint.
compose	function	Composes functions right-to-left: `compose(f, g)(x)` is equivalent to `f(g(x))`.
consoleLogPromise	promise	Returns a function that logs data to the console and passes it through.
contains	geometry	Whether a point or a rectangle is inside a rectangle.
contrastRatio	color	Computes the WCAG 2 contrast ratio between two colors, from 1 (identical) to 21 (black on white).
correctFloat	number	Corrects floating-point arithmetic errors by rounding to a given number of significant digits.
countBy	array	Groups the elements of an array by the key returned by `keyFn` and returns a record mapping each key to the number of m…
countBy	map	Groups the entries of a Map by a derived key and counts how many fall into each group.
countBy	set	Groups the values of a Set by a derived key and counts how many fall into each group.
createBackStack	structure	Creates a back stack: a stack that always has a current entry (the one on top), with the previous ones underneath to go…
createByteReader	binary	Creates a cursor over bytes, for decoding binary formats: fixed-size integers and floats, LEB128 varints (signed ones z…
createByteWriter	binary	Creates a growable buffer to encode binary formats: the counterpart of createByteReader, with the same types, byte orde…
createCachedResolver	function	Creates a lazy, cached resolver: `resolve(key)` computes and caches `compute(key)` the first time a given key is seen,…
createFileStore	browser	Creates a file store on a named Cache API cache: keep a computed set of files (a bake, a download, extracted layers) un…
createGlobMatcher	string	createMatcher with every string read as a glob (`*`, `?`): no string is ever taken for a regular expression, so it neve…
createMatcher	string	Turns user-supplied filters (a setting, a CLI flag, a list of rules) into one predicate.
createMutex	promise	Creates a mutex: a lock allowing at most one holder at a time, queueing excess `acquire()` callers in FIFO order.
createRegexMatcher	string	createMatcher with every string read as the source of a regular expression, without slashes or flags (`’^(Home|Login)$’…
createSafeMatcher	string	Like createMatcher, but returns `null` instead of throwing when a string pattern is an invalid regular expression, to r…
createSemaphore	promise	Creates a semaphore limiting concurrent access to `permits` holders at a time, queueing excess `acquire()` callers in F…
createSortByBooleanFn	array	Creates a sort function for objects by a boolean property.
createSortByDateFn	array	Creates a sort function for objects by date property.
createSortByNaturalFn	array	Creates a sort function for objects by one or more string properties using natural ordering.
createSortByNumberFn	array	Creates a sort function for objects by number property.
createSortByStringFn	array	Creates a sort function for objects by one or more string properties.
createUnionFind	structure	Creates a disjoint-set (union-find) structure: tracks a partition of items into non-overlapping sets, merging two sets…
cubicBezier	animation	Builds the easing function of CSS `cubic-bezier(x1, y1, x2, y2)`: given the progress of time (`0` to `1`), it returns t…
curry	function	Transforms a multi-argument function into a chain of single-argument functions (Haskell-style currying).
daysInMonth	date	Returns the number of days in the given month of the given year.
DebianDependency	package	One package reference of a Debian relationship field: `name[:arch] [(op version)] [[archs]] []`.
DebianDependencyOptions	package	Options of the Debian format of parseDependencies.
DebianOperator	package	The operators of a Debian version constraint (Debian Policy 7.1): `<<` (strictly earlier), `<=`, `=`, `>=` and `>>` (st…
debounce	function	Creates a debounced function that delays invoking func until after delay milliseconds have elapsed since the last time…
decodeImage	browser	Loads an image and waits until it is decoded, so it can be painted without a flash or a decoding pause (e.g.
dedent	string	Strips the common leading whitespace from every line of a multi-line string, and trims a single leading/trailing blank…
DeepGet	type	Resolves the value type at a given `Path` within `T`.
DeepPartial	type	Recursively makes all properties of T optional, including nested objects and array elements.
DeepSet	type	Produces the type of `T` after replacing the value at `Path` with `V`.
DeepWritable	type	Recursively removes `readonly` from all properties of T, including nested objects, array elements, and tuple positions.
DEFAULT_PERCENTAGE_TIERS	ci	Default tiers, geared towards coverage/quality-gate style percentages.
defer	promise	Runs an async function and guarantees that all deferred callbacks are executed afterwards, in LIFO order (last register…
delay	promise	Creates a promise that resolves after specified delay
deobfuscate	string	Reverses obfuscate.
DependencyConstraint	package	A version constraint such as the `(>= 2.34)` of `libc6 (>= 2.34)`, with the operator spelled as the format spells it.
diff	object	Structural object diff.
difference	array	Returns the difference between two arrays (items in first array but not in second).
difference	date	Calculates the difference between two dates in the specified unit.
difference	set	native JS Set.prototype.difference() (ES2025 (Set methods))
distance	geography	Great-circle distance between two WGS84 points, in kilometres (haversine formula, mean Earth radius of 6371 km).
drop	array	native JS Array.prototype.slice(n) (ES3)
eachDay	date	Returns an array of `Date` objects for each day from `start` to `end` (inclusive).
eachMonth	date	Returns an array of `Date` objects for the first day of each month from `start` to `end` (inclusive).
ellipsePath	geometry	The path of the ellipse that fills a box, as SVG path data: two half-turn arcs.
endOf	date	Returns a new `Date` set to the **end** of the given unit.
ensureArray	array	Wraps a value in an array if it is not already one.
ensureDate	date	Safely converts a date-like value to a valid `Date` object, or returns `null`.
equalsDeep	array	Recursive structural array equality.
equalsDeep	object	Recursive structural object equality.
equalsShallow	array	Positional, one-level (shallow) array equality.
equalsShallow	object	One-level (shallow) object equality.
equalsUnordered	array	Order-independent (set-style) array equality.
escape	markdown	Escapes all Markdown special characters in a string so they render as literal text rather than formatting syntax.
escapeHtml	string	Escapes the HTML special characters `&`, `<`, `>`, `”`, and `’` in a string.
escapeRegExp	string	Escapes regular expression metacharacters (`.
every	map	Checks if every entry of a Map satisfies the predicate.
excerpt	string	Derives a short, readable excerpt from a longer text — for a card/header/preview where a full paragraph doesn’t fit.
extractErrorMessage	string	Convert an error to a readable message.
extractNumber	number	Extracts the first number embedded anywhere in a string, or passes through a `number`.
extractPureURI	url	Extracts the pure URI from a URL by removing query parameters and fragments.
falsyPromiseOrThrow	promise	Returns a function that passes through falsy data or throws an error.
families	license	Groups a raw, possibly compound license string into its coarse family set — e.g.
fetchJson	fetch	Fetches a URL and returns its parsed JSON body, retrying transient failures.
fetchJson	promise	Fetches a URL and returns its parsed JSON body, retrying transient failures (network errors, `5xx` and `429`).
fetchOrThrow	fetch	Wraps `fetch` so that a non-2xx response rejects with an HttpError, instead of resolving like any other response — the…
fetchOrThrow	promise	Wraps `fetch` so that a non-2xx response rejects with an HttpError.
filter	map	Creates a new Map containing only the entries for which the predicate returns true.
filter	set	Creates a new Set containing only the values for which the predicate returns true.
filterAsync	array	The async counterpart to `Array.prototype.filter`: runs `predicate` for every item and resolves to the items whose pred…
find / findIndex	array	native JS Array.prototype.find() / findIndex() (ES2015)
findKey	map	Returns the first key of a Map whose entry satisfies the predicate, in insertion order.
findKey / findValue	map	native JS map.entries().find(([k, v]) => pred(v, k))?.[0 or 1] (ES2025 (Iterator Helpers))
findMap	array	Returns the first non-`undefined` result of mapping `fn` over `array`, short-circuiting as soon as one is found.
findValue	map	Returns the first value of a Map whose entry satisfies the predicate, in insertion order.
fit	geometry	Places content in a box like CSS `object-fit` and `object-position`, e.g.
fitContain	geometry	Places content in a box, as large as possible while staying entirely inside the box (CSS `object-fit: contain`).
fitCover	geometry	Places content in a box, as small as possible while covering the whole box (CSS `object-fit: cover`).
fitFill	geometry	Places content in a box, stretched to the box on each axis, without keeping its proportions (CSS `object-fit: fill`).
fitNone	geometry	Places content in a box, at its own size, only positioned (CSS `object-fit: none`).
fitScaleDown	geometry	Places content in a box, like fitContain, but never enlarged (CSS `object-fit: scale-down`).
flatten	object	Flattens a nested object into a single-level object whose keys are the dot-notation path to each leaf value.
flatten / flat	array	native JS Array.prototype.flat(depth?) (ES2019)
flip	function	Creates a function that invokes `fn` with the first two arguments swapped.
forEach	map	native JS Map.prototype.forEach((value, key, map) => ...) (ES2015)
forEach	set	native JS Set.prototype.forEach((value, value2, set) => ...) (ES2015)
forEachAsync	array	The async counterpart to `Array.prototype.forEach`: runs `fn` for every item for its side effects, discarding any retur…
format	date	Formats a date as a short label that does not depend on the machine: UTC, English, and `Jul 27, 2026` by default.
formatCompact	number	Formats a number using compact notation (e.g.
formatDuration	date	Formats a duration in milliseconds as a compact human-readable string.
formatInTimezone	date	Formats a date in a specific IANA timezone using `Intl.DateTimeFormat`.
formatPartial	date	Formats a partial ISO date at the precision it was given, in UTC: a year alone is approximate and reads `c.
formatPath	geometry	Writes path commands back as SVG path data: letters and numbers separated by single spaces, numbers rounded to `precisi…
formatProgressBar	string	Formats a value as a text progress bar, repeating `filledChar`/`emptyChar` across `width` cells proportional to `value…
formatSize	number	Format a byte count into a human-readable string with the appropriate unit.
frameLoop	animation	Calls `onFrame` once per animation frame with the time elapsed since the start, until it returns `false` or the loop is…
from (parse temporal string)	date	native JS Temporal.Instant.from(str) / Temporal.PlainDate.from(str) / etc. (Temporal (Stage 3))
fromBase64	string	Decodes Base64 text.
fromMillis	date	Creates a `Date` from a timestamp in **milliseconds**.
fromSeconds	date	Creates a `Date` from a timestamp in **seconds**.
get	object	Gets a value from an object using a dot/bracket-notated path or explicit key array.
getTimezoneOffset	date	Returns the UTC offset **in minutes** for the given IANA timezone at a specific point in time.
globToRegExp	string	Compiles a glob pattern into a `RegExp` that matches the whole string.
groupBy	map	native JS Map.groupBy(map.entries(), ([k, v]) => groupFn(v, k)) (ES2024)
groupBy	object	Groups an array of items by a key derived from each item.
groupBy	set	native JS Map.groupBy(set.values(), fn) (ES2024)
groupBy / group	array	native JS Object.groupBy(arr, fn) (ES2024)
guard	promise	Wraps a function so that if it throws, a default value is returned instead of propagating the error.
has	object	native JS Object.hasOwn(obj, key) (ES2022)
hasValue	map	Checks whether a value exists anywhere in a Map (`Map.prototype.has` checks keys, not values).
hasValue	map	native JS map.values().some(v => Object.is(v, value)) (ES2025 (Iterator Helpers))
head / first	array	native JS Array.prototype.at(0) (ES2022)
hexToRgb	color	Parses a hex color string (`#rgb`, `#rgba`, `#rrggbb`, `#rrggbbaa` — the leading `#` is optional) into its RGB(A) chann…
hsbToRgb	color	Converts an HSB(A) color (also called HSV), as shown by design tool color pickers, into RGB(A).
hslToCss	color	Formats an HSL(A) color as a CSS `hsl()` value, in the modern space-separated syntax.
hslToRgb	color	Converts an HSL(A) color into RGB(A).
identity	function	Returns the given value unchanged Useful as a default transform, in function composition, or as a placeholder mapper.
identity	geometry	The matrix that changes nothing.
includes	array	native JS Array.prototype.includes() (ES2016)
increment	version	Increments a version, according to the given `scheme`.
incrementPrerelease	version	Increments the prerelease portion of a version, according to the given `scheme` — the semantics `npm version prerelease…
injectWordBreaks	string	Adds word-break opportunities to a string so it can wrap cleanly in narrow UI containers such as side panels or table c…
inRange	number	Checks whether a number falls within `[min, max]` (both inclusive by default).
interpolate	animation	Blends two values of the same shape: every number goes from its value in `from` (`t = 0`) to its value in `to` (`t = 1`…
intersection	array	Compute the intersection of two arrays, meaning the elements that are present in both arrays.
intersection	geometry	The area two rectangles have in common.
intersection	set	native JS Set.prototype.intersection() (ES2025 (Set methods))
intersects	array	Simple helper that check if two lists shared at least an item in common.
intersects	geometry	Whether two rectangles have an area in common, exactly when intersection returns a rectangle: rectangles that only touc…
invert	geometry	The matrix that undoes `m`, e.g.
invert	object	Returns a new object with keys and values swapped.
isArray	guard	Checks if a value is an array.
isArrayBuffer	guard	Checks if a value is an ArrayBuffer instance.
isArrayLike	guard	Checks if a value is array-like: has a non-negative integer `length` property.
isAsyncFunction	guard	Checks if a value is an async function.
isAsyncGenerator	guard	Checks if a value is an async generator object (the result of calling an `async function*`).
isAsyncGeneratorFunction	guard	Checks if a value is an async generator function (an `async function*` declaration or expression).
isAsyncIterable	guard	Checks if a value implements the async iterable protocol.
isBigInt	guard	Checks if a value is a bigint.
isBlank	string	Checks if a string is blank — empty or contains only whitespace characters.
isBlob	guard	Checks if a value is a Blob instance.
isBoolean	guard	Checks if a value is a boolean.
isBrowser	guard	Checks whether the code is currently running in a browser-like environment (`window` and `window.document` both defined…
isBuffer	node	Checks if a value is a Node.js Buffer instance.
isBusinessDay	date	Checks whether a date falls on a business day (i.e.
isCanonicalJson	guard	Checks whether a value is a string that is already canonical JSON (RFC 8785, JSON Canonicalization Scheme) — byte for b…
isConventionalCommit	commit	Checks whether a commit message’s subject line follows the Conventional Commits format constrained by the given options.
isCssColor	guard	Checks whether a value is a syntactically-safe, plain CSS color: a hex color (`#rgb`, `#rgba`, `#rrggbb`, `#rrggbbaa`),…
isDate	guard	Checks if a value is a Date instance.
isDefined	guard	Checks if a value is defined (not undefined nor null).
isDirectInstanceOf	type	native JS value.constructor === Foo (ES1)
isEmpty	array	Checks if an array is empty (has no elements).
isEmpty	object	Checks if a plain object has no own enumerable string-keyed properties.
isEmpty	string	Checks if a string is empty (`""`), `null`, or `undefined`.
isError	guard	Checks if a value is an Error instance.
isEven	number	Checks if a value is an even integer.
isExternal	url	Whether a link points to another origin than `base`: an absolute `http(s)` URL or a protocol-relative one (`//host/path…
isFalsy	guard	Checks if a value is falsy (`false`, `null`, `undefined`, `0`, `""`, `NaN`).
isFinite / isFiniteNumber	type	native JS Number.isFinite(value) (ES2015)
isFormData	guard	Checks if a value is a FormData instance.
isFunction	guard	Checks if a value is a function.
isGenerator	guard	Checks if a value is a generator object (the result of calling a `function*`).
isGeneratorFunction	guard	Checks if a value is a generator function (a `function*` declaration or expression).
isHostname	guard	Checks whether a value is a syntactically valid DNS hostname (RFC 952, RFC 1123, RFC 3696 section 2).
isHtmlElement / isUrlInstance / isUrlSearchParams	type	native JS value instanceof HTMLElement / URL / URLSearchParams (Web API)
isIJson	guard	Checks whether a value is a string holding I-JSON (RFC 7493, the Internet JSON message format): strict JSON that every…
isInfinite	type	native JS value === Infinity || value === -Infinity / !Number.isFinite(value) && !Number.isNaN(value) (ES2015)
isInteger	type	native JS Number.isInteger(value) (ES2015)
isIterable	guard	Checks if a value is iterable (has a `Symbol.iterator` method).
isJSON	guard	Checks whether a value is a string containing valid, parseable JSON text.
isJson5	guard	Checks whether a value is a string holding valid JSON5 (JSON5 1.0.0) — JSON with comments, trailing commas, unquoted ke…
isJSONArray	guard	Checks whether a value is an array whose every element is a valid JSON value (see isJSONValue).
isJsonc	guard	Checks whether a value is a string holding valid JSONC — JSON with comments and trailing commas, the dialect of `tsconf…
isJSONObject	guard	Checks whether a value is a plain object whose every own value is a valid JSON value (see isJSONValue).
isJsonSequence	guard	Checks whether a value is a string holding a valid JSON text sequence (RFC 7464, `application/json-seq`): records that…
isJSONValue	guard	Checks whether a value is composed entirely of JSON-representable types: `string`, finite `number`, `boolean`, `null`,…
isKnown	license	Whether a raw license string resolves to at least one recognized family — `false` for an empty string, a purely non-inf…
isLeapYear	date	Returns `true` if the given year is a leap year.
isLength	guard	Checks whether a value is a valid array-like `length`: a non-negative safe integer (`0 <= value <= Number.MAX_SAFE_INTE…
isLight / isDark (pick a readable text color)	color	native JS contrast-color(<color>) (CSS Color 6 (Baseline newly available since April 2026 — Chrome 147, Firefox 146, Safari 26.0))
isMap	guard	Checks if a value is a Map instance.
isNaN	type	native JS Number.isNaN(value) (ES2015)
isNdjson	guard	Checks whether a value is a string holding valid newline-delimited JSON — one strict JSON value per line, as NDJSON and…
isNegative	number	Checks if a value is a number less than 0.
isNode	guard	Checks whether the code is currently running in a Node.js-like environment (`process.versions.node` is defined — also t…
isNodeStream	node	Checks if a value is a Node.js stream (has a `.pipe()` method).
isNonEmpty	array	Checks if an array is non-empty (has at least one element).
isNonEmpty	object	Checks if a plain object has at least one own enumerable string-keyed property.
isNonEmpty	string	Checks if a string is non-empty (has at least one character).
isNotBlank	string	Checks if a string is not blank — non-empty and contains at least one non-whitespace character.
isNull	guard	Checks if a value is `null`.
isNullish	guard	Checks if a value is null or undefined (nullish).
isNumber	guard	Checks if a value is a number.
isObservable	observable	Checks if a value is an RxJS Observable or any compatible observable.
isOdd	number	Checks if a value is an odd integer.
isoWeek	date	ISO 8601 week of a date: weeks start on Monday and week 1 is the one that contains the first Thursday of the year, so t…
isPlainObject	guard	Checks if a value is a plain object.
isPositive	number	Checks if a value is a number greater than 0.
isPrerelease	version	Returns `true` when the version string has a prerelease suffix, according to the given `scheme`.
isPrimitive	guard	Checks if a value is a JavaScript primitive.
isPromise	guard	Checks if a value is a Promise or a thenable.
isPromiseLike	guard	Checks if a value is a thenable (has a `.then()` method).
isPropertyKey	guard	Checks if a value is a valid property key: `string`, `number`, or `symbol`.
isRegExp	guard	Checks if a value is a RegExp instance.
isSafeInteger	type	native JS Number.isSafeInteger(value) (ES2015)
isSameDay	date	Checks if two dates are the same day.
isSameMonth	date	Checks if two dates are in the same month (and year).
isSameYear	date	Checks if two dates are in the same year.
isSet	guard	Checks if a value is a Set instance.
isSet (Set data structure)	type	native JS value instanceof Set (ES2015)
isSharedArrayBuffer	node	Checks if a value is a `SharedArrayBuffer` instance.
isSpecialObject	guard	Determines if a value is a special object that should not have its properties compared deeply.
isString	guard	Checks if a value is a string.
isSymbol	guard	Checks if a value is a symbol.
isTemporalDuration	guard	Checks if a value is a `Temporal.Duration`.
isTemporalInstant	guard	Checks if a value is a `Temporal.Instant`.
isTemporalPlainDate	guard	Checks if a value is a `Temporal.PlainDate`.
isTemporalPlainDateTime	guard	Checks if a value is a `Temporal.PlainDateTime`.
isTemporalPlainTime	guard	Checks if a value is a `Temporal.PlainTime`.
isTemporalZonedDateTime	guard	Checks if a value is a `Temporal.ZonedDateTime`.
isTimestamp	guard	Checks if a value is a valid timestamp (milliseconds or Unix seconds).
isTimestampInSeconds	date	Checks if a timestamp is likely in seconds (Java/Unix style) vs milliseconds (JavaScript style)
isTruthy	guard	Checks if a value is truthy (not `false`, `null`, `undefined`, `0`, `""`, or `NaN`).
isUndefined	guard	Checks if a value is `undefined`.
isValid	date	Checks if a value is a valid Date instance (not `Invalid Date`).
isValid	version	Whether `version` is a valid version in the given `scheme`.
isValidDateString	date	Checks whether a string can be parsed into a valid `Date`.
isValidRegex	guard	Checks if a string is a valid regex pattern.
isWeakMap	guard	Checks if a value is a WeakMap instance.
isWeakMap / isWeakSet / isWeakRef	type	native JS value instanceof WeakMap / WeakSet / WeakRef (ES2015 / ES2021)
isWeakMapKey	guard	Checks whether a value can be used as a key in a `WeakMap` (or a `WeakSet` member / `WeakRef` target) — an object, a fu…
isWeakSet	guard	Checks if a value is a WeakSet instance.
isWeekend	date	Checks whether a date falls on a weekend day.
isWithinDistance	geography	Whether a point lies within a radius of a center, the border included.
isWithinRange	date	Checks whether a date falls within a range (inclusive on both ends).
kebabCase	string	Converts a string to kebab-case.
kebabCaseKeys	object	Recursively transforms every key of a plain object (including keys nested inside arrays and nested objects) to kebab-ca…
keys / values	object	native JS Object.keys() / Object.values() (ES2017)
KeysOfType	type	Extracts the keys of `T` whose values extend `V`.
last	array	native JS Array.prototype.at(-1) (ES2022)
leadingSentence	string	Extracts the leading sentence from a string.
lerp	number	Linearly interpolates between `start` and `end` by the factor `t`.
levenshteinDistance	string	Levenshtein edit distance between two strings — the minimum number of single-character insertions, deletions, or substi…
levenshteinSimilarity	string	Normalized Levenshtein similarity between two strings, in `[0, 1]` — `1` means identical, `0` means completely dissimil…
lighten / darken	color	native JS color-mix(in oklch, <color> <percent>, white|black) (CSS Color 5 (Baseline widely available since 2023 — Chrome 111, Firefox 113, Safari 16.2))
listTimezones	date	Returns the list of IANA timezone identifiers supported by the runtime.
loadFont	browser	Loads a font and registers it in `document.fonts`, so CSS and canvas can use `family` right away.
map	object	Transforms the values and/or keys of a plain object in a single pass.
map	set	Creates a new Set with each value transformed by a function.
map / filter	set	native JS new Set(set.values().map(fn)) / new Set(set.values().filter(fn)) (ES2025 (Iterator Helpers))
mapAsync	array	The async counterpart to `Array.prototype.map`: applies `fn` to every item and resolves to an array of the results, in…
mapDeep	object	Recursively transforms the keys and/or values of a plain object — the deep counterpart to map, which only transforms th…
mapKeys	map	Creates a new Map with the same values but with each key transformed by a function.
mapSettled	array	Like mapAsync, but never rejects: each item gets its own result, in the shape of `Promise.allSettled`, so one failure d…
mapValues	map	Creates a new Map with the same keys but with each value transformed by a function.
matchesMedia	browser	Whether the document currently matches a CSS media query.
matchGlob	string	Whether `text` matches a glob pattern in full: `*` matches any run of characters, `?` exactly one.
matrixToCss	geometry	Writes a matrix as a CSS `transform` or SVG `transform` value.
max	array	Returns the maximum value in an array using a loop instead of spread, avoiding the call stack overflow that occurs with…
maxBy	array	Returns the element of an array with the greatest derived key, computed by `keyFn`.
Maybe	type	Type for values that can be T, undefined, or null.
mean	array	Calculates the arithmetic mean (average) of an array of numbers.
meanBy	array	Calculates the arithmetic mean of numbers derived from each item of an array via an iteratee.
meaningPromiseOrThrow	promise	Returns a function that passes through meaningful data or throws an error.
median	array	Calculates the median (middle value) of an array of numbers.
mediaTypeOf	binary	Finds the media type of an image from its first bytes (its magic number), whatever its name says: PNG, JPEG, GIF, WebP,…
mediaTypeOfPath	binary	Finds the media type of a file from the extension of its path or URL: images, fonts, web documents, scripts and styles,…
memoize	function	Returns a memoized version of the function that caches results.
merge (shallow)	object	native JS { ...a, ...b } or Object.assign({}, a, b) (ES2015)
mergeDeep	object	Merges two or more objects deeply, returning a **new** object without mutating any input.
min	array	Returns the minimum value in an array using a loop instead of spread, avoiding the call stack overflow that occurs with…
min / max	number	native JS Math.min(...arr) / Math.max(...arr) (ES1)
minBy	array	Returns the element of an array with the smallest derived key, computed by `keyFn`.
mixColors	color	Mixes two colors in sRGB, as CSS `color-mix(in srgb, color P%, base)` does: `percent`% of `color` and the rest of `base…
multiply	geometry	Multiplies matrices, in the mathematical order: the last one applies first.
negate	function	Creates a function that negates the result of `predicate`.
noop	function	A no-operation function that does nothing and returns `undefined` Useful as a default callback, placeholder, or to exp…
normalizeTimestamp	date	Converts a timestamp to JavaScript milliseconds format
now (date/time/instant)	date	native JS Temporal.Now.instant() / .zonedDateTimeISO() / .plainDateISO() / .plainTimeISO() (Temporal (Stage 3))
Nullable	type	Adds `null` to a type (`T | null`).
Nullish	type	Adds `null` and `undefined` to a type (`T | null | undefined`).
obfuscate	string	Hides a text from anything that reads the raw page source: the text is reversed (by Unicode code point, so emoji stay w…
observeIntersection	browser	Calls `callback` each time `element` enters or leaves the viewport (or `options.root`), with an `IntersectionObserver`…
observeResize	browser	Calls `callback` each time the size of `element` changes, with a `ResizeObserver` dedicated to it.
omit	object	Creates a new object without the specified keys.
omitBy	object	Creates a new object without the own enumerable entries for which `predicate` returns `true`.
OmitByValue	type	Constructs a type by omitting all entries of `T` whose values extend `V`.
once	function	Creates a function that is restricted to be called only once.
onlyPath	url	Extract only the path from an URI with optional query and fragments.
onPointerIntent	browser	Tells a tap from a drag, and hover from touch, on one element: the pointer-event logic every draggable or clickable wid…
OptionalKeys	type	Extracts the optional keys of an object type `T`.
overlaps	date	Checks whether two date ranges overlap.
padStart / padEnd	string	native JS String.prototype.padStart() / padEnd() (ES2017)
paginate	promise	Collects every item of a paginated source by requesting pages one after the other, from page 1, until the source runs o…
parallel	promise	Runs an array of async functions with a concurrency limit.
parallelSettle	promise	Runs an array of async functions with a concurrency limit, partitioning the outcomes instead of rejecting on the first…
parse	json	Parses JSON permissively: strict JSON, JSONC (the dialect of `tsconfig.json` and VS Code’s `settings.json`, also known…
parse	version	Parses a version string into its components, according to the given `scheme`.
parseConventionalCommit	commit	Parses a Conventional Commits message into a structured object.
parseDeb822	package	Parses a deb822 document, the format of Debian `Packages`, `Sources` and `Release` indexes, `control` and `.dsc` and `.…
parseDependencies	package	Parses the value of a package dependency field (`Depends`, `Requires`, `depends`, …) into a structure: groups of alte…
parseDuration	date	Parses a compact duration string (as produced by formatDuration, e.g.
ParsedVersion	version	A version parsed according to SemVer 2.0.0 — alias of ParsedSemVerVersion, kept under this name for backward compatibil…
parseEasing	animation	Reads a CSS easing into an easing function, to play in JavaScript the timing a stylesheet or a design tool export descr…
parseLines	json	Parses newline-delimited JSON — one JSON value per line.
parsePackageRepository	url	Parse the `repository` field from `package.json` into a structured object.
parsePartial	date	Parses an ISO date that may only be known to the year or the month: `YYYY`, `YYYY-MM` or `YYYY-MM-DD`.
parsePath	geometry	Parses SVG path data (the `d` attribute) into commands, as written: the letters keep their case (absolute or relative),…
parsePatternOrRegExp	string	Reads a setting that is either a regular expression or a glob: `/source/flags` is a regular expression when every flag…
parsePropertyPath	object	Parses a dot/bracket-notation property path into an array of string/number key segments — the same notation accepted by…
parseSequence	json	Parses a JSON text sequence (RFC 7464, `application/json-seq`): records that each start with the ASCII record separator…
parseStrict	json	Parses strict JSON (RFC 8259) — exactly what `JSON.parse` accepts, nothing more.
partial	function	Partially applies arguments to a function, returning a new function that accepts the remaining arguments.
partition	array	Splits an array into two groups based on a predicate function.
pascalCase	string	Converts a string to PascalCase.
pascalCaseKeys	object	Recursively transforms every key of a plain object (including keys nested inside arrays and nested objects) to PascalCa…
Pep508Dependency	package	One requirement of a PEP 508 dependency specification.
Pep508Operator	package	The operators of a PEP 440 version specifier, as PEP 508 requirements use them.
percentageToTier	ci	Maps a numeric percentage to a tier (icon, color, label) using configurable thresholds.
percentile	array	Calculates the p-th percentile of an array of numbers using linear interpolation between the closest ranks.
pick	object	Creates a new object with only the specified keys.
pickBy	object	Creates a new object with only the own enumerable entries for which `predicate` returns `true`.
PickByValue	type	Constructs a type by picking all entries of `T` whose values extend `V`.
pickClosest	font	Picks the face that CSS would use for a request, among the faces of one family: the CSS Fonts Level 4 matching algorith…
pipe	function	Composes functions left-to-right: the output of each function is passed as input to the next.
prefersReducedMotion	browser	Whether the user asked the system to reduce motion (`prefers-reduced-motion: reduce`).
preloadImages	browser	Loads and decodes several images with decodeImage, a few at a time, with `mapSettled` from `helpers4/array`.
premultiply	color	Multiplies the color channels by the alpha channel (premultiplied alpha), the form compositing and GPU blending work in.
Prettify	type	Flattens an intersection type into a single readable object type.
randomBetween	number	Generates a random number between min and max (inclusive)
randomIntBetween	number	Generates a random integer between min and max (inclusive)
range	array	Generates an array of sequential numbers from start to end (exclusive).
rectToRect	geometry	The translation and scale that put one rectangle exactly on another, for animating or fitting between two boxes.
reduce	map	Reduces a Map to a single value by applying a function to each entry, in insertion order.
reduce / some / every	map	native JS map.entries().reduce(fn, init) / .some(fn) / .every(fn) (ES2025 (Iterator Helpers))
reduce / some / every / find	set	native JS set.values().reduce(fn, init) / .some(fn) / .every(fn) / .find(fn) (ES2025 (Iterator Helpers))
reflectAttribute	browser	Defines a property on `element` that is backed by an HTML attribute — what a custom element needs for `<my-card heading…
relativeLuminance	color	Computes the WCAG 2.x relative luminance of a color: the perceived brightness from 0 (black) to 1 (white), after linear…
relativeURLToAbsolute	url	Converts a relative URL to an absolute URL, using `base` when given, or else the current document base URI (and the win…
removeDiacritics	string	Removes diacritical marks (accents) from a string, e.g.
removeUndefinedNull	object	Remove null and undefined values from an object.
repeat	string	native JS String.prototype.repeat() (ES2015)
replaceOrAppend	array	Returns a new array with the first item matching `predicate` replaced by `item` — or `item` appended at the end if no m…
requestWorker	browser	Runs one job in a module worker: starts it, posts the request, relays its progress, resolves with its result and ends i…
RequiredKeys	type	Extracts the required (non-optional) keys of an object type `T`.
resolveRecord	promise	Resolves an array of keys into a record by calling an async mapper for each key.
retry	promise	Retries a promise-returning function until it succeeds or runs out of attempts, then rejects with the last error, waiti…
returnOrThrowError	function	Return a value or throw an error if null or undefined.
reverse	array	native JS Array.prototype.toReversed() (ES2023)
reverseSortFn	array	Reverses the order of a sort function: `reverseSortFn(fn)(a, b)` is `fn(b, a)`.
rgbToCss	color	Formats an RGB(A) color as a CSS `rgb()` value, in the modern space-separated syntax that every current browser and SVG…
rgbToHex	color	Converts an RGB(A) color into a hex color string.
rgbToHsb	color	Converts an RGB(A) color into HSB(A), the model design tools (Figma, Sketch, XD) show in their color pickers.
rgbToHsl	color	Converts an RGB(A) color into HSL(A).
rgbToUnit	color	Converts an RgbColor (channels from `0` to `255`) into a color whose channels are floats from `0` to `1`, the way Figma…
rotate	geometry	A matrix that rotates points around the origin.
roundedRectPath	geometry	The path of a rectangle with a radius per corner, as SVG path data.
roundTo	number	Rounds a number to specified decimal places
RpmDependency	package	One package reference of an RPM `Requires` field.
safeFetch	fetch	Wraps `fetch` with built-in error handling: returns `null` when the request fails (network error, non-OK status, or par…
safeFetch	promise	Wraps `fetch` and returns `null` when the request fails (network error, non-OK status, or parse error) instead of throw…
safeJsonParse	object	Parses a JSON string, returning `null` (or a fallback) on any parse failure.
safeParse	json	Parses JSON permissively like parse — strict JSON, JSONC (HuJSON, JWCC) and JSON5 — but returns `null` (or `fallback`)…
safeParseLines	json	Parses newline-delimited JSON (NDJSON, JSON Lines) like parseLines, but returns `null` (or `fallback`) instead of throw…
safeParseSequence	json	Parses a JSON text sequence (RFC 7464) like parseSequence, but returns `null` (or `fallback`) instead of throwing on in…
safeParseStrict	json	Parses strict JSON like parseStrict, but returns `null` (or `fallback`) instead of throwing on invalid input.
safeReadJsonFile	node	Reads a file and parses its contents as JSON, returning `null` (or a fallback) on any failure — a missing/unreadable fi…
sample	array	Picks one or more random elements from an array.
satisfiesRange	version	Checks if a version satisfies a range, according to the given `scheme` (simple implementation — see each scheme’s own d…
scale	geometry	A matrix that scales points from the origin.
select	array	Filters and transforms an array in a single pass.
select / filterMap	array	native JS Array.prototype.filter().map() (ES5)
set	object	Sets a value in an object at the given path, creating intermediate objects as needed.
settle	promise	Runs an array of promises concurrently and partitions the outcomes instead of rejecting on the first failure, unlike `P…
sha256Hex	browser	The SHA-256 digest of some data as a hexadecimal string, optionally cut short: a compact content key, not a security ch…
shuffle	array	Randomly reorders elements of an array using the Fisher-Yates algorithm.
simplifyPolyline	geometry	Removes the points of a polyline that change its shape by less than `tolerance`, with the Ramer–Douglas–Peucker algorit…
slugify	string	Converts a string into a URL-friendly slug.
snakeCase	string	Converts a string to snake_case.
snakeCaseKeys	object	Recursively transforms every key of a plain object (including keys nested inside arrays and nested objects) to snake_ca…
some	map	Checks if at least one entry of a Map satisfies the predicate.
sort (immutable)	array	native JS Array.prototype.toSorted(compareFn?) (ES2023)
sortBy / orderBy	array	native JS Array.prototype.toSorted(fn?) (ES2023)
sortKeys	object	Creates a new object with the same entries as the input, but with its own keys sorted.
sortNumberAscFn	array	Sort numbers in ascending order
sortNumberDescFn	array	Sort numbers in descending order
sortStringAscFn	array	Sort strings in ascending order
sortStringAscInsensitiveFn	array	Sort strings in ascending order (case insensitive)
sortStringDescFn	array	Sort strings in descending order
sortStringNaturalAscFn	array	Sort strings in ascending order using natural (human-friendly) ordering.
sortStringNaturalAscInsensitiveFn	array	Sort strings in ascending natural order, ignoring case **and diacritics** (`Intl.Collator { sensitivity: ‘base’ }` — tr…
sortStringNaturalDescFn	array	Sort strings in descending order using natural (human-friendly) ordering.
sortStringNaturalDescInsensitiveFn	array	Sort strings in descending natural order, ignoring case **and diacritics** (`Intl.Collator { sensitivity: ‘base’ }` — t…
sortVersions	version	Sorts version strings by version, not by text (`1.10.0` after `1.9.0`), in the given scheme: the same as `versions.sort…
spring	animation	Simulates a damped spring going from `0` to `1`, the curve behind “spring” transitions of design tools, and computes ho…
startOf	date	Returns a new `Date` set to the **start** of the given unit.
startsWith / endsWith	string	native JS String.prototype.startsWith() / endsWith() (ES2015)
statusToBadge	ci	Maps a CI/CD job status to an inline code badge string.
statusToIcon	ci	Maps a CI/CD job status to an emoji icon.
steps	animation	Builds the easing function of CSS `steps(count, position)`: progress moves by jumps instead of continuously, for frame-…
stringify	json	Serializes a value to JSON text — pretty-printed with 2 spaces by default, or canonical.
stringify	version	Reconstructs a version string from a AnyParsedVersion object — the scheme is read from the object’s own `scheme` field,…
stringifyDependencies	package	Writes dependency groups back as a field value, the inverse of parseDependencies;
stringifyForHtml	json	Serializes a value to compact JSON that is safe to inline in an HTML page, typically in a `<script type=“application/js…
stringifyLines	json	Serializes values as newline-delimited JSON — one compact JSON value per line, each followed by `\n`.
stringifySequence	json	Serializes values as a JSON text sequence (RFC 7464, `application/json-seq`): each value is written as the ASCII record…
stripHtml	string	Plain text of an HTML fragment: tags removed, `
stripV	version	Strip the leading “v” from a version string if it exists.
sum	array	Calculates the sum of an array of numbers.
sumBy	array	Calculates the sum of numbers derived from each item of an array via an iteratee.
symmetricDifference	array	Returns the symmetric difference between two arrays: items present in exactly one of the two arrays (in either, but not…
symmetricDifference	set	native JS Set.prototype.symmetricDifference() (ES2025 (Set methods))
tail	array	native JS Array.prototype.slice(1) (ES3)
take	array	native JS Array.prototype.slice(0, n) (ES3)
template	string	Interpolates `{{key}}` placeholders in a template string with values from a data record.
throttle	function	Creates a throttled function that only invokes func at most once per every wait milliseconds Call `cancel()`, or abort…
timeAgo	date	Formats a date as a human-readable relative time string.
timeout	promise	Wraps a promise to reject with a `TimeoutError` if it does not resolve within the specified duration.
titleCase	string	Converts a string to Title Case.
titleCaseKeys	object	Recursively transforms every key of a plain object (including keys nested inside arrays and nested objects) to Title Ca…
toBase64	string	Encodes a string (as UTF-8) or raw bytes to Base64, without relying on `btoa` or `Buffer`, so it behaves the same in a…
toCssLinear	animation	Samples an easing function into a CSS `linear()` easing, so any curve (a spring, a custom bounce) can be played by CSS…
toggle	array	Returns a new array with `item` removed if present, or appended if absent — the common “toggle a selection” pattern.
toHex	binary	Writes bytes as lowercase hexadecimal, two digits per byte.
toInt / toFloat	number	native JS parseInt(str, 10) / parseFloat(str) (ES1)
toISO8601	date	Converts a date to ISO 8601 format Format: YYYY-MM-DDTHH:mm:ss.sssZ
toMapByKey	map	Builds a Map from an iterable of items, keyed by a derived key.
toMapByKey	set	Builds a Map from a Set, keyed by a derived key.
toMillis	date	Converts a date to a timestamp in **milliseconds** (epoch millis).
toPairs / fromPairs	object	native JS Object.entries() / Object.fromEntries() (ES2019)
toPlainDate / toPlainDateTime / toPlainTime	date	native JS Temporal.ZonedDateTime.prototype.toPlainDate() / toPlainDateTime() / toPlainTime() (Temporal (Stage 3))
toRFC2822	date	Converts a date to RFC 2822 format Format: Day, DD Mon YYYY HH:mm:ss +0000 Used in email headers (Date field) and HTTP…
toRFC3339	date	Converts a date to RFC 3339 format Format: YYYY-MM-DDTHH:mm:ssZ or YYYY-MM-DDTHH:mm:ss+HH:mm RFC 3339 is a profile of I…
toSeconds	date	Converts a date to a timestamp in **seconds** (epoch seconds).
toTemporalInstant	date	native JS Date.prototype.toTemporalInstant() (Temporal (Stage 3))
toZonedDateTime	date	native JS Temporal.Instant.prototype.toZonedDateTimeISO(tz) (Temporal (Stage 3))
transformPath	geometry	Transforms SVG path data by a matrix.
translate	geometry	A matrix that moves points by `(tx, ty)`.
trim	string	Trims both leading and trailing characters from a string, at a configurable level of aggressiveness (see TrimMode).
trim / trimStart / trimEnd	string	native JS String.prototype.trim() / trimStart() / trimEnd() (ES2019)
trimEnd	string	Trims trailing characters from a string, at a configurable level of aggressiveness (see TrimMode).
trimStart	string	Trims leading characters from a string, at a configurable level of aggressiveness (see TrimMode).
truncate	string	Truncates a string to `maxLength` characters, appending an ellipsis when cut.
truthyPromiseOrThrow	promise	Returns a function that passes through truthy data or throws an error.
tryit	promise	Wraps a function so it never throws.
tween	animation	Animates a value from `from` to `to` over `durationMs`, calling `onUpdate` with the blended value at each frame, for wh…
TypedArrays (isInt8Array, isFloat32Array, ...)	type	native JS value instanceof Int8Array / Float32Array / ... (ES2015)
unary	function	Creates a function that calls `fn` with only its first argument, discarding any others.
unescapeHtml	string	Unescapes the HTML entities `&`, `<`, `>`, `”`, and `&#39;` back to `&`, `<`, `>`, `”`, and `’`.
unflatten	object	Rebuilds a nested object from a single-level object whose keys are dot-notation paths.
union	array	native JS unique([...a, ...b]) (ES2015)
union	geometry	The smallest rectangle that contains all the given rectangles, e.g.
union	set	native JS Set.prototype.union() (ES2025 (Set methods))
UnionToIntersection	type	Converts a union type to an intersection type: `A | B | C` → `A & B & C`.
unique	array	Removes duplicate values from an array.
uniqueBy	array	Removes duplicate items from an array, using a derived key instead of value equality.
unitToRgb	color	Converts a color whose channels are floats from `0` to `1` (as Figma, Sketch and Penpot store them) into an RgbColor, w…
unorderedPairKey	string	Builds a canonical, order-independent key for an unordered pair of strings — the same result for `(a, b)` and `(b, a)`.
unpremultiply	color	Divides the color channels by the alpha channel: the inverse of premultiply.
unset	object	Removes the value at a dot/bracket-notation path or explicit key array, mutating the object in place.
until / since (difference)	date	native JS Temporal.PlainDate.prototype.until(other) / .since(other) (Temporal (Stage 3))
unzip	array	Splits an array of tuples into separate arrays, one per position.
update	object	Updates the value at a path by applying a function to its current value, creating intermediate objects as needed.
uuid7	id	Generates a UUID v7 string (RFC 9562).
ValueOf	type	Produces a union of all value types of an object type `T`.
watchMedia	browser	Calls `listener` each time a CSS media query starts or stops matching.
WeekDays	date	Named day-of-week constants following the JavaScript `Date.getDay()` convention.
whenIdle	browser	Runs `callback` when the browser is idle, with `requestIdleCallback`, for work that can wait (prefetching, analytics, w…
withAlpha (change the alpha channel of an existing color)	color	native JS rgb(from <color> r g b / <alpha>) (CSS Color 5 relative color syntax (Baseline widely available since September 2024 — Chrome 119+))
withLeadingSlash	url	Adds a leading slash `/` to the given URL if it is not already present.
without	array	Returns a new array with all occurrences of the given values removed.
withoutLeadingSlash	url	Removes the leading slash `/` from the given URL if it is present.
withoutTrailingSlash	url	Removes the trailing slash `/` from the given URL if it is present.
withResolvers	promise	native JS Promise.withResolvers() (ES2024)
withTempDir	node	Creates a fresh temporary directory under the OS temp root, runs `fn` with its path, and always removes it (recursively…
withTrailingSlash	url	Adds a trailing slash `/` to the given URL if it is not already present.
words	string	Splits a string into an array of words.
zigzagDecode	binary	The inverse of zigzagEncode: maps an unsigned 64-bit zigzag value back to the signed integer.
zigzagEncode	binary	Maps a signed 64-bit integer to an unsigned one so that values near zero stay small (`0, -1, 1, -2` become `0, 1, 2, 3`…
zip	array	Combines multiple arrays element-by-element into an array of tuples.