[转] 考验你的JavaScript底细

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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" ）