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# which-boxed-primitive <sup>[![Version Badge][2]][1]</sup> | |
[![dependency status][5]][6] | |
[![dev dependency status][7]][8] | |
[![License][license-image]][license-url] | |
[![Downloads][downloads-image]][downloads-url] | |
[![npm badge][11]][1] | |
Which kind of boxed JS primitive is this? This module works cross-realm/iframe, does not depend on `instanceof` or mutable properties, and works despite ES6 Symbol.toStringTag. | |
## Example | |
```js | |
var whichBoxedPrimitive = require('which-boxed-primitive'); | |
var assert = require('assert'); | |
// unboxed primitives return `null` | |
// boxed primitives return the builtin constructor name | |
assert.equal(whichBoxedPrimitive(undefined), null); | |
assert.equal(whichBoxedPrimitive(null), null); | |
assert.equal(whichBoxedPrimitive(false), null); | |
assert.equal(whichBoxedPrimitive(true), null); | |
assert.equal(whichBoxedPrimitive(new Boolean(false)), 'Boolean'); | |
assert.equal(whichBoxedPrimitive(new Boolean(true)), 'Boolean'); | |
assert.equal(whichBoxedPrimitive(42), null); | |
assert.equal(whichBoxedPrimitive(NaN), null); | |
assert.equal(whichBoxedPrimitive(Infinity), null); | |
assert.equal(whichBoxedPrimitive(new Number(42)), 'Number'); | |
assert.equal(whichBoxedPrimitive(new Number(NaN)), 'Number'); | |
assert.equal(whichBoxedPrimitive(new Number(Infinity)), 'Number'); | |
assert.equal(whichBoxedPrimitive(''), null); | |
assert.equal(whichBoxedPrimitive('foo'), null); | |
assert.equal(whichBoxedPrimitive(new String('')), 'String'); | |
assert.equal(whichBoxedPrimitive(new String('foo')), 'String'); | |
assert.equal(whichBoxedPrimitive(Symbol()), null); | |
assert.equal(whichBoxedPrimitive(Object(Symbol()), 'Symbol'); | |
assert.equal(whichBoxedPrimitive(42n), null); | |
assert.equal(whichBoxedPrimitive(Object(42n), 'BigInt'); | |
// non-boxed-primitive objects return `undefined` | |
assert.equal(whichBoxedPrimitive([]), undefined); | |
assert.equal(whichBoxedPrimitive({}), undefined); | |
assert.equal(whichBoxedPrimitive(/a/g), undefined); | |
assert.equal(whichBoxedPrimitive(new RegExp('a', 'g')), undefined); | |
assert.equal(whichBoxedPrimitive(new Date()), undefined); | |
assert.equal(whichBoxedPrimitive(function () {}), undefined); | |
assert.equal(whichBoxedPrimitive(function* () {}), undefined); | |
assert.equal(whichBoxedPrimitive(x => x * x), undefined); | |
assert.equal(whichBoxedPrimitive([]), undefined); | |
``` | |
## Tests | |
Simply clone the repo, `npm install`, and run `npm test` | |
[1]: https://npmjs.org/package/which-boxed-primitive | |
[2]: https://versionbadg.es/inspect-js/which-boxed-primitive.svg | |
[5]: https://david-dm.org/inspect-js/which-boxed-primitive.svg | |
[6]: https://david-dm.org/inspect-js/which-boxed-primitive | |
[7]: https://david-dm.org/inspect-js/which-boxed-primitive/dev-status.svg | |
[8]: https://david-dm.org/inspect-js/which-boxed-primitive#info=devDependencies | |
[11]: https://nodei.co/npm/which-boxed-primitive.png?downloads=true&stars=true | |
[license-image]: https://img.shields.io/npm/l/which-boxed-primitive.svg | |
[license-url]: LICENSE | |
[downloads-image]: https://img.shields.io/npm/dm/which-boxed-primitive.svg | |
[downloads-url]: https://npm-stat.com/charts.html?package=which-boxed-primitive |