Why is typeof null “object”?

Question

I\'m reading \'Professional Javascript for Web Developers\' Chapter 4 and it tells me that the five types of primitives are: undefined, null, boolean, number and string.

Answer 1

If null is a primitive, why does typeof(null) return "object"?

Because the spec says so.

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

1. Let val be the result of evaluating UnaryExpression.
2. If Type(val) is Reference, then
      a. If IsUnresolvableReference(val) is true, return "undefined".
      b. Let val be GetValue(val).
3. Return a String determined by Type(val) according to Table 20.