An initially confusing and counter-intuitive behavior of JavaScript is that the type determination of a variable being null using typeof returns "object".
var demo = null;
typeof demo; // "object"
The reason for this is that typeof will always return "object" for native non-callable objects. Actually, this stands since the beginning of JavaScript and the operator simply returns the type string of a given reference according to the table specified in the ECMAScript language specification ECMA-262 (see page 81).
A fix that would have resulted in typeof null === "null" has been proposed (via an opt-in), but was rejected as it was too late to fix the "problem" as a change of typeof null would break existing code like incorrect implementations of type checks.
