typeOf

A smart replacement of the typeof operator and robust type checker. This is my first ever published module on npm (2017). I have rewritten it to the modern stack (TypeScript, Vitest) without functional changes.

Installation

pnpm add @everget/typeof

Usage

const typeOf = require('@everget/typeof');
// or
import typeOf from '@everget/typeof';

let value = 'awesome string';

typeOf(value)();
// => 'string'

typeOf(value) == 'string';
// => true

typeOf(value).expect('string');
// => true

typeOf(value).expect('number');
// => TypeError: The value is of type `string`, but expected `number`

/** NOTE: you must use `==` operator for correct work */
let isMap = (value) => typeOf(value)() == 'map';

let smth = new Map();

if (isMap(smth)) {
  /** Do your staff */
}

let isFunction = (value) => {
  return typeOf(value).expect('function|asyncfunction|generatorfunction');
}

let smth = async () => {};

if (isFunction(smth)) {
  /** Do your staff */
}

function sum(a, b) {
  typeOf(a).expect('number');
  typeOf(b).expect('number');

  return typeOf(a + b).expect('number') && (a + b);
}

sum(1, () => {});
// => TypeError: The value is of type `function`, but expected `number`

sum(1, 2);
// => 3

Examples of returned values

ES

Value | Type ----------------------------------- | ---- {} | 'object' Math | 'math' JSON | 'object' function() {} | 'function' [] | 'array' null | 'null' (function() { return arguments })() | 'arguments' new Error | 'error' undefined | 'underfined'

ES6, ES7

Value | Type ----------------------------- | ---- Reflect | 'object' class {} | 'function' Proxy | 'function' new Proxy({}, {}) | 'object' () => {} | 'function' function* () {} | 'generatorfunction' async function() {} | 'asyncfunction' Symbol | 'function' Symbol() | 'symbol' new Map | 'map' new WeakMap | 'weakmap' new Set | 'set' new WeakSet | 'weakset' [1, 2, 3].entries() | 'arrayiterator' new Set().entries() | 'setiterator' new Map().entries() | 'mapiterator' ''Symbol.iterator | 'stringiterator' new ArrayBuffer() | 'arraybuffer' new DataView(new ArrayBuffer) | 'dataview'

Browser

Value | Type ---------------------------------- | ---- window | 'global' document | 'htmldocument' localStorage | 'storage' new DOMException | 'domexception' document.createDocumentFragment() | 'documentfragment' document.createElement('a') | 'htmlanchorelement' document.createElement('body') | 'htmlbodyelement' document.createElement('template') | 'htmltemplateelement' document.createTextNode('') | 'text' document.createComment('') | 'comment'

Node.js

Value | Type ------- | ---- global | 'global' process | 'process'

Tests

npm test

Release History

• 0.1.0 Initial release
• 0.1.1 Added detection of typed arrays
• 2.0.0 Corrections for global object, Math, JSON, async functions and generators
• 3.0.0 Implemented new usage syntax. Added correct detection of iterators