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which-boxed-primitive

1.0.1 • Public • Published

which-boxed-primitive Version Badge

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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

var whichBoxedPrimitive = require('which-boxed-primitive');
var assert = require('assert');
 
// unboxed primitives return `null`
// boxed primitives return the builtin contructor 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

Install

npm i which-boxed-primitive

DownloadsWeekly Downloads

740,774

Version

1.0.1

License

MIT

Unpacked Size

20.1 kB

Total Files

10

Last publish

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