3.1.0 • Published 3 months ago

valid-types

Licence

MIT

Version

3.1.0

Deps

Size

70 kB

Vulns

Weekly

Stars

Summary Dependency Versions

valid-types

A lightweight, zero-dependency JavaScript/TypeScript type-checking utility. Provides reliable type guards for all built-in JS types, including edge cases like NaN, arguments, async functions, and ES6+ types (Map, Set, Promise, Symbol, etc.).

Installation

npm install valid-types
# or
yarn add valid-types

Usage

import { isString, isNumber, isArray } from 'valid-types';

isString('hello');   // true
isNumber(42);        // true
isArray([1, 2, 3]);  // true

CommonJS is also supported:

const { isString } = require('valid-types');

API

Primitives

Function	Description	Example
`isString(value)`	`true` for string primitives	`isString('hi')` → `true`
`isNumber(value)`	`true` for finite numbers (excludes `NaN`)	`isNumber(NaN)` → `false`
`isBoolean(value)`	`true` for `true` / `false`	`isBoolean(1)` → `false`
`isNull(value)`	`true` only for `null`	`isNull(null)` → `true`
`isUndefined(value)`	`true` only for `undefined`	`isUndefined(undefined)` → `true`
`isDefined(value)`	`true` for anything except `undefined`	`isDefined(null)` → `true`
`isNan(value)`	`true` only for `NaN` (not string `"NaN"`)	`isNan(NaN)` → `true`
`isSymbol(value)`	`true` for symbol primitives	`isSymbol(Symbol())` → `true`

Objects

Function	Description	Example
`isObject(value)`	`true` for plain objects only (not `null`, `Array`, `Date`, etc.)	`isObject({})` → `true`
`isArray(value)`	`true` for arrays	`isArray([])` → `true`
`isDate(value)`	`true` for `Date` instances	`isDate(new Date())` → `true`
`isRegExp(value)`	`true` for `RegExp` instances	`isRegExp(/abc/)` → `true`
`isMap(value)`	`true` for `Map` instances	`isMap(new Map())` → `true`
`isSet(value)`	`true` for `Set` instances	`isSet(new Set())` → `true`
`isError(value)`	`true` for `Error` and subclasses	`isError(new TypeError())` → `true`
`isArguments(value)`	`true` for `arguments` objects (not array-likes)	—

Functions

Function	Description	Example
`isFunction(value)`	`true` for regular and arrow functions only	`isFunction(() => {})` → `true`
`isClass(value)`	`true` for ES6 class declarations	`isClass(class Foo {})` → `true`
`isAsync(value)`	`true` for async functions (not Promise instances)	`isAsync(async () => {})` → `true`
`isPromise(value)`	`true` for `Promise` instances	`isPromise(Promise.resolve())` → `true`

Strings & URLs

Function	Description	Example
`isUrl(value)`	`true` for valid `http:`, `https:`, or `ftp:` URLs	`isUrl('https://example.com')` → `true`
`isBase64(value)`	`true` for base64 data URLs (`data:...;base64,...`)	`isBase64('data:image/png;base64,abc')` → `true`

Empty checks

Function	Description	Example
`isEmpty(value)`	`true` for `''`, `0`, `'0'`, `null`, `false`, `undefined`	`isEmpty('')` → `true`
`isEmptyObject(value)`	`true` for plain objects with no own keys	`isEmptyObject({})` → `true`
`isEmptyArray(value)`	`true` for arrays with no elements	`isEmptyArray([])` → `true`

Generic

Function	Returns	Example
`isType(value)`	String type name	`isType(new Map())` → `'map'`

Possible return values: 'string', 'number', 'NaN', 'boolean', 'undefined', 'null', 'symbol', 'object', 'array', 'date', 'regexp', 'map', 'set', 'error', 'promise', 'function', 'class', 'async', 'arguments', 'dom', 'document'

TypeScript

All functions ship with full TypeScript support. Where possible they are typed as proper type guards:

function processInput(value: unknown) {
  if (isString(value)) {
    // value is string here
    console.log(value.toUpperCase());
  }

  if (isArray(value)) {
    // value is unknown[] here
    value.forEach(console.log);
  }
}

Development

# run tests
npm test

# build
npm run build

# lint
npm run lint

# format
npm run format

License

MIT

Keywords

type-check types validation