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Changelog

[3.0.0] 2026-09-30 Changed (3) · Breaking (types only) (1) · Added (2) · Docs (1)

The runtime is byte-for-byte the same: no predicate returns a different value for any input. This is a major release because the types are now stricter, and stricter narrowing breaks a common pattern (see Breaking (types only)).

Changed

  • Twelve checkers are now TypeScript type predicates (value is T), so tsc narrows in both branches. Every checker’s parameter is unknown instead of any.

    FunctionPredicate
    isStringvalue is string
    isPlainObjectvalue is Record<string, unknown>
    isObjectvalue is object
    isDatevalue is Date
    isRegexvalue is RegExp
    isPromisevalue is Promise<unknown>
    isIterablevalue is Iterable<unknown>
    isGeneratorvalue is IterableIterator<unknown> (duck-typed: next() plus self-iterable; Generator’s return/throw are not verified)
    isScalarvalue is string | boolean | number | symbol | bigint
    isPrimitivevalue is string | boolean | number | bigint
    isFormElementvalue is HTMLFormElement (falls back to object when the DOM lib is not in the consumer’s compilation, so the typings never require lib: ["dom"])
    isFormDatavalue is FormData (falls back to object when FormData is not declared)

  • Kept as plain boolean, on purpose: isInt, isFloat, isNumeric, isJson, isUrl, isEmail, isValidId, isEmpty and the environment checks. These accept a subset of their base type, so a predicate would narrow the false branch wrongly: with n: number, if (isInt(n)) {} else { n } would make n never although 1.5 takes the else branch. isNumeric additionally accepts numeric strings and single-element arrays (String([5]) === "5"), so neither number nor number | `${number}` would be true. isEmpty is not a test for one type.

  • Known limits of the predicates, documented in the README: isObject returns false for functions although Function is assignable to object; isRegex checks constructor.name === "RegExp", so a RegExp subclass under another class name returns false.

Breaking (types only)

  • A value typed any is narrowed by a type predicate. Code such as if (isPlainObject(data)) { data.user.name } (with data: any, e.g. a JSON.parse result) compiled before and now fails with 'data.user' is of type 'unknown'; the same applies to isObject, isIterable and isPromise on any. Type the value (const data: Payload), or narrow further after the guard. No runtime change, no change for unknown- or union-typed values.

Added

  • Exported helper types: ScalarValue, PrimitiveValue, FormElementType, FormDataType.
  • Type-level tests (src/__tests__/types.test-d.ts, expectTypeOf, run by vitest typecheck mode) and runtime narrowing tests (src/__tests__/guards.test.ts). npm run test:types runs tsc --noEmit.

Docs

  • README, llms.txt, llms-full.txt and the skills describe the predicates and the boolean-only checkers. They previously claimed isString (or nothing) was a type guard.

Tests

102 runtime tests across 6 files + 6 type-level tests (types.test-d.ts) = 108
[2.1.4] 2026-08-17 Security (1)

Security

  • isValidId regex is now linear (src/index.ts:50). The previous pattern nested a quantified group inside another quantifier, giving a match cost that grows quadratically-to-exponentially in the input length — so a long crafted string passed to Is.validHtmlId(...) pinned the thread instead of returning false. A validator is exactly the surface that gets pointed at untrusted input, which is what makes this worth a release. The pattern is now /^[A-Za-z][\w\-:.]*$/: a single unambiguous character class with no nested quantifier, so there is nothing to backtrack over. Accepted and rejected values are unchanged.
[2.1.3] 2026-05-26 Fixed (18) · Added (5) · Changed (10) · Removed (2)

Fixed

  • isNumeric — stateful regex (src/index.ts:10). Dropped the /g flag so RegExp.prototype.test no longer advances lastIndex between calls. Repeated calls on the same input now return a stable true.
  • isInt — rejects negative integers (src/index.ts:16). Replaced the regex with Number.isInteger(value) so signed integers are accepted.
  • isInt — rejects integers in scientific notation (src/index.ts:16). Same fix — Number.isInteger(1e21) correctly returns true.
  • isFloat — rejects negative floats / unescaped . in regex (src/index.ts:22). Regex is now /^-?\d+\.\d+$/ (sign branch + escaped .), gated on Number.isFinite so NaN/Infinity are rejected.
  • isObject, isRegex, isPlainObject, isPromise, isDate, isGenerator, isIterable — non-boolean falsy returns (multiple lines). Predicates now coerce with Boolean(...) / explicit value !== null checks instead of leaking the raw falsy value (null, undefined, 0, "").
  • isPlainObject — throws on Object.create(null) (src/index.ts:39). Now short-circuits to true when the prototype is null; otherwise falls back to the constructor?.name === "Object" check with an optional chain.
  • isPromise — doesn’t recognize subclasses (src/index.ts:79). Switched to value instanceof Promise, which accepts subclasses while still rejecting bare thenables.
  • isGenerator — never matches a generator instance (src/index.ts:91). Replaced the constructor-name check with a duck-typed test: object + .next function + self-iterable (value[Symbol.iterator]() === value).
  • isEmpty — returns true for non-empty plain objects (src/index.ts:103). Added an Object.keys(value).length === 0 fast-path for non-iterable plain objects, so { a: 1 } is now correctly reported as non-empty.
  • isEmpty — returns true for new Date() (src/index.ts:103). Constructed Date instances now short-circuit to false.
  • isEmpty — returns true for NaN (src/index.ts:103). NaN is now treated as non-empty (it’s still a numeric value).
  • isIterable — returns the empty string instead of true for "" (src/index.ts:64). Replaced the truthy guard with explicit null/undefined checks so the empty string flows through to the Symbol.iterator test.
  • isUrl — accepts trailing dots and .. (src/index.ts:142). Hostname is now split on . and rejected if any label is empty, so https://google. and https://google..com both return false.
  • isEmail — matches single-element arrays (src/index.ts:160). Added a typeof value === "string" guard before the regex test, so arrays / non-strings can’t sneak through via String() coercion.
  • isSafari — false-positives on class-based DOM polyfills (src/index.ts:273). Replaced the /constructor/i.test(window.HTMLElement) heuristic with a userAgent-based detector that requires Safari AND excludes Chrome|Chromium|Edg|OPR|Android.
  • isOpera — references bare opr global (src/index.ts:288). Switched to window.opr?.addons so the predicate no longer risks a ReferenceError in strict mode.
  • isBrowser — duplicated buggy logic for safari / opera (src/index.ts:243). The function now delegates to isChrome(), isFirefox(), isSafari(), isOpera(), isIE(), isEdge() instead of inlining (and re-introducing) the same bugs.
  • isMobile.any — circular self-reference through Is (src/index.ts:232). Replaced Is.mobile.X() calls with direct isMobile.X() calls so the object no longer depends on its own export being initialized.

Added

  • README.md — marketing-style index with a 30-second tour, a categorized predicate table, an isEmpty semantics section, an SSR-safety note, and a curated list of known bugs.
  • CHANGELOG.md — this file.
  • AI kit — llms.txt, llms-full.txt, and skills/ cards (README, overview, primitives, collections, formats, misc, environment, recipes).
  • Test suite — 89 passing tests across primitives, collections, formats, misc, and environment. The suite uses Vitest under happy-dom so DOM-touching predicates (isFormElement, isFormData, isMobile.*, isMac, isBrowser, isChrome/isFirefox/isSafari/isOpera/isIE/isEdge) can be exercised with a configurable navigator.userAgent.
  • CI — GitHub Actions matrix: Node 18 / 20 / 22 on Ubuntu plus Node 20 on Windows.

Changed

  • Test runner: Jest → Vitest. Tests moved from tests/ to src/__tests__/ (matches @mongez/atom’s layout) and are organized by category (primitives.test.ts, collections.test.ts, formats.test.ts, misc.test.ts, environment.test.ts).
  • package.json:
    • Description rewritten to actually describe the package (“tree-shakable type & shape predicates”).
    • Added sideEffects: false so bundlers can drop unused exports for real.
    • Keyword list expanded from 10 generic terms to a comprehensive index of every exported predicate.
    • Removed Jest config block.
    • devDependencies: dropped jest, ts-jest, @types/jest, jest-esm-jsx-transform; bumped typescript to ^5.4; added vitest@^2.1 and happy-dom@^15.
  • Dropped dev dependencies: jest, ts-jest, @types/jest, jest-esm-jsx-transform. The package no longer carries a Jest config.
  • Added dev dependencies: vitest@^2.1, happy-dom@^15.
  • Bumped: typescript@^4.5 → ^5.4.

Removed

  • tests/ directory (replaced by src/__tests__/).
  • Stale devDeps listed above.

Tests

89 passing + 0 skipped = 89 total across 5 files