[置顶] 考考你们的JS 我只作对了一半你们试试

最新推荐文章于 2021-06-03 16:44:17 发布

原创最新推荐文章于 2021-06-03 16:44:17 发布 · 248 阅读

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JavaScript 同时被 3 个专栏收录

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编程

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面试

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本文通过一系列JavaScript代码片段，探讨了变量类型判断、特殊值处理及函数行为等关键概念。通过对NaN、null、undefined等类型的深入分析，以及对函数作用域、闭包特性的考察，帮助读者更好地理解JavaScript的工作原理。

alert(typeof(NaN)); 

alert(typeof(Infinity));

alert(typeof(null)); 

alert(typeof(undefined)); 

alert(NaN==NaN); 

alert(NaN!=NaN); 

alert(NaN>NaN);  

alert(null==undefined);  

alert(null>=undefined);  

alert(null<=undefined);  

alert(null==null);

alert(null!=null); 

alert(null!=NaN); 

alert(null==NaN);

alert(NaN==undefined); 

alert(parseInt("123abc"));

alert("123abc"-0); 

alert(Infinity>10); 

alert(Infinity>"abc"); 

alert(Infinity==NaN);

alert(true==1); 

alert(new String("abc")=="abc"); 

alert(new String("abc")==="abc"); 

 
function step(a){

   return function(x){

      return x+a++;

   }

}

var a = step(10);

var b = step(20);

alert(a(10));

alert(b(20));

var a="123abc";

alert(typeof(a++));

alert(a);

用这个面试估计死掉一大批啊

更新下新的我错了8题

    1.


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

        “object”
        “array”
        “arguments”
        “undefined”
    2.


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

        “number”
        “undefined”
        “function”
        Error
    3.


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

        1
        null
        undefined
        Error
    4.


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

        1
        “number”
        undefined
        “undefined”
    5.


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

        “number”
        “undefined”
        “function”
        Error
    6.


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

        “undefined”
        “object”
        “number”
        “function”
    7.


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

        “undefined”
        “object”
        “number”
        “function”
    8.


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

        “string”
        “number”
        “function”
        “undefined”
    9.


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

        1
        “1function”
        “1undefined”
        NaN
    10.


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

        “number”
        “string”
        “undefined”
        “object”
    11.


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

        “undefined”
        “object”
        “number”
        Error
    12.


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

        1
        2
        Error (e.g. “Too much recursion”)
        undefined
    13.


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

        true
        false
    14.


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

        1
        2
        undefined
        Error