Fun with JavaScript variable types and constructors

Try running the following code in Firebug (the results are shown in trailing comments):

console.log(typeof null); // object
console.log(null instanceof Object); // false
console.log(typeof [1,2,3]); // object
console.log(typeof /regex/); // function in Firefox; object in IE
console.log(typeof new String()); // object
console.log(typeof Object); // function
console.log(Object instanceof Object); // true
console.log(Object instanceof Function); // true
console.log(Function.constructor); // Function()
console.log(Function.constructor.constructor); // Function()
console.log(window.constructor); // function() [note the lowercase "f"]
console.log(window.constructor.constructor); // Object()
console.log(window.constructor.constructor.constructor); // Function()
console.log(Function()); // anonymous()

console.log(typeof NaN); // number
console.log(NaN.constructor); // Number()
console.log(NaN instanceof Number); // false
console.log(NaN == NaN); // false
console.log(null + 1); // 1
console.log(null + null); // 0
console.log(undefined + 1); // NaN
console.log(null + "string"); // nullstring
console.log(undefined + "string"); // undefinedstring
console.log({} == 0); // false
console.log([] == 0); // true
console.log(1.0.toFixed(2)); // 1.00

console.log(new Boolean(false) == false); // true
console.log(new Boolean(false) === false); // false

Surprised by any of those results? If not, you're probably either quite knowledgeable about JavaScript variable types, type conversion, and constructors, or you don't fully understand some of the peculiarities and seeming contradictions. (If you have any questions, feel free to ask in the comments.)