Inspecting internal [[class]] of objects in JS

.js

// NOTE: this is specification dependent classification. It has nothing to do with formal class programming concept.
// The value of the [[Class]] internal property is defined by specification for every kind of built-in object.
// The value of the [[Class]] internal property of a host object may be any String value except one of:
// "Arguments", "Array", "Boolean", "Date", "Error", "Function", "JSON", "Math", "Number", "Object", "RegExp", and "String". 
// The value of a [[Class]] internal property is used internally to distinguish different kinds of objects. 

Object.prototype.toString.call({}); //           "[object Object]"
Object.prototype.toString.call([]); //           "[object Array]"
Object.prototype.toString.call(function(){}); // "[object Function]"
Object.prototype.toString.call(''); //           "[object String]"
Object.prototype.toString.call(0); //            "[object Number]"
Object.prototype.toString.call(true); //         "[object Boolean]"
Object.prototype.toString.call(/''/); //         "[object RegExp]"
Object.prototype.toString.call(new Date); //     "[object Date]"
Object.prototype.toString.call(new Error); //    "[object Error]"
Object.prototype.toString.call(Math); //         "[object Math]"
Object.prototype.toString.call(JSON); //         "[object JSON]"
Object.prototype.toString.call(function(){return arguments;}()); // "[object Arguments]"