http://sentsin.com/

尽管今日的JavaScript已经突飞猛进，但JS的许多特性仍然保留，以下题目并不是有意设坑，许多地方将验证你的JS底细，如果错了一半，请别告诉我你从事前端。

1. 1.

   (function(){  return typeof arguments;})();

   • "object"
   • "array"
   • "arguments"
   • "undefined"
2. 2.

   var f = function g(){   return 23; };typeof g();

   • "number"
   • "undefined"
   • "function"
   • Error
3. 3.

   (function(x){  delete x;  return x;})(1);

   • 1
   • null
   • undefined
   • Error
4. 4.

   var y = 1, x = y = typeof x;x;

   • 1
   • "number"
   • undefined
   • "undefined"
5. 5.

   (function f(f){  return typeof f();})(function(){ return 1; });

   • "number"
   • "undefined"
   • "function"
   • Error
6. 6.

   var foo = {  bar: function() {    return this.baz;   },  baz: 1};(function(){  return typeof arguments[0]();})(foo.bar);

   • "undefined"
   • "object"
   • "number"
   • "function"
7. 7.

   var foo = {  bar: function(){    return this.baz;   },  baz: 1}typeof (f = foo.bar)();

   • "undefined"
   • "object"
   • "number"
   • "function"
8. 8.

   var f = (  function f(){     return "1";   },   function g(){     return 2;   })();typeof f;

   • "string"
   • "number"
   • "function"
   • "undefined"
9. 9.

   var x = 1;if (function f(){}) {  x += typeof f;}x;

   • 1
   • "1function"
   • "1undefined"
   • NaN
10. 10.

    var x = [typeof x, typeof y][1];typeof typeof x;

    • "number"
    • "string"
    • "undefined"
    • "object"
11. 11.

    (function(foo){  return typeof foo.bar;})({ foo: { bar: 1 } });

    • "undefined"
    • "object"
    • "number"
    • Error
12. 12.

    (function f(){  function f(){ return 1; }  return f();  function f(){ return 2; }})();

    • 1
    • 2
    • Error (e.g. "Too much recursion")
    • undefined
13. 13.

    function f(){ return f; }new f() instanceof f;

    • true
    • false
14. 14.

    with (function(x, undefined){}) length;

    • 1
    • 2
    • undefined
    • Error

思考题：如何改变 undefined的typeof类型 ? （即 typeof undefined 或者 typeof(undefined) 都不为"undefined" ）