Which kind of boxed JS primitive is this? This module works cross-realm/iframe, does not depend oninstanceof or mutable properties, and works despite ES6 Symbol.toStringTag.
varwhichBoxedPrimitive=require('which-boxed-primitive');varassert=require('assert');// unboxed primitives return `null`// boxed primitives return the builtin constructor nameassert.equal(whichBoxedPrimitive(undefined),null);assert.equal(whichBoxedPrimitive(null),null);assert.equal(whichBoxedPrimitive(false),null);assert.equal(whichBoxedPrimitive(true),null);assert.equal(whichBoxedPrimitive(newBoolean(false)),'Boolean');assert.equal(whichBoxedPrimitive(newBoolean(true)),'Boolean');assert.equal(whichBoxedPrimitive(42),null);assert.equal(whichBoxedPrimitive(NaN),null);assert.equal(whichBoxedPrimitive(Infinity),null);assert.equal(whichBoxedPrimitive(newNumber(42)),'Number');assert.equal(whichBoxedPrimitive(newNumber(NaN)),'Number');assert.equal(whichBoxedPrimitive(newNumber(Infinity)),'Number');assert.equal(whichBoxedPrimitive(''),null);assert.equal(whichBoxedPrimitive('foo'),null);assert.equal(whichBoxedPrimitive(newString('')),'String');assert.equal(whichBoxedPrimitive(newString('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(newRegExp('a','g')),undefined);assert.equal(whichBoxedPrimitive(newDate()),undefined);assert.equal(whichBoxedPrimitive(function(){}),undefined);assert.equal(whichBoxedPrimitive(function*(){}),undefined);assert.equal(whichBoxedPrimitive(x=>x*x),undefined);assert.equal(whichBoxedPrimitive([]),undefined);
