在JavaScript中，如果数组，函数是对象原型，那么为什么typeof返回

Question

在javascript中，如果数组是函数，则函数是对象原型，那么为什么typeof为包含数组的变量返回对象，而对于包含对函数的引用的变量返回Function。

Answer 1

Per the ECMAScript 3.0 specification (Pages 46 - 47):

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

1. Evaluate UnaryExpression.
2. If Type(Result(1)) is not Reference, go to step 4.
3. If GetBase(Result(1)) is null , return "undefined" .
4. Call GetValue(Result(1)).
5. Return a string determined by Type(Result(4)) according to the following table:

Type                                              Result
Undefined                                         "undefined"
Null                                              "object"
Boolean                                           "boolean"
Number                                            "number"
String                                            "string"
Object (native and doesn’t implement [[Call]])    "object"
Object (native and implements [[Call]])           "function"
Object (host)                                     Implementation-dependent

I couldn't find any reference to typeof in the 1.0 specification, and while wikipedia references a 2.0 specification, I couldn't find it online.

While georg makes a lovely sentiment, it would appear that the typeof unary operator was added to JavaScript sometime after the initial release (so some thought had to have been put into it).

That said, there are many ways around the limitations. Just google " fixing typeof "... there's around 41.7 million results. :)