The JavaScript typeof Operator Problem
TL;DR don't even try to normalize or shim newer typeof via code: you simply can't! Whenever it was a mistake or not to consider typeof null == "object" , many libraries that tried to normalize this operator failed to understand that null is not the only problem . The JS Polymorphism Nature We can borrow methods for basically everything but primitives values, such booleans, numbers, and strings, do not accept indeed any sort of property or method attached runtime. var s = "hello"; s.greetings = true; alert(s.greetings); // "undefined" However, we can still use methods through call() or apply() : function isGreetings() { return /^(?:ciao|hello|hi)$/.test(this); } alert(isGreetings.call("hello")); // true The only way to find a method in a primitive value is to extend its own constructor.prototype : String.prototype.isGreetings = function () { return /^(?:ciao|hello|hi)$/.test(this); }; alert("hello".isGreetings()); // tru...