JavaScript预解析、作用域题目记录

拼搏现实的明天。 2022-10-19 00:53 228阅读 0赞

## JavaScript预解析、作用域题目记录 ##

**写出以下题目执行的结果及过程分析**

function fun ( n ) { 
      console.log( n );
      var n = 456;
      console.log( n );
    }
    var n = 123;
    fun( n );

![在这里插入图片描述][20210708204909621.png]

function fun () { 
      console.log( n );
      var n= 456;
      console.log( n );
    }
    var n = 123;
    fun( n );

![在这里插入图片描述][20210708205150101.png]

function fun () { 
      console.log( n );
      n = 456;
      console.log( n );
    }
    var n= 123;
    fun( n);
    console.log( n );

![在这里插入图片描述][20210708205430457.png]

var n = 123;
    function f1 () { 
      console.log( n ); //作用域为window
    }
    function f2 () { 
      var n = 456;
      f1();
    }
    f2();
    console.log( n );

![在这里插入图片描述][20210708205718601.png]

![在这里插入图片描述][20210708210116213.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaG1vbmtleQ_size_16_color_FFFFFF_t_70]

function f() { 
        console.log( this.a )
    }
    var obj = { 
        a: 2,
        f: f
    }
    var f2 = obj.f; 
    var a = "hello world"; 
    f2();

![在这里插入图片描述][20210708210349924.png]

function f( something ) { 
        console.log( this.a, something)
        return this.a + something
    }
    var obj = { 
        a: 2
    }
    var f2 = function() { 
        return f.apply( obj, arguments)  //arguments--3
    }
    var b = f2(3); 
    console.log(b);

![在这里插入图片描述][20210708210607599.png]

[20210708204909621.png]: /images/20221005/ecc4ecd806214508b1d1653a9a0f97fc.png
[20210708205150101.png]: /images/20221005/2f8a5e91afde4b48bf1815c4406ddde3.png
[20210708205430457.png]: /images/20221005/c2245ee026884e8abdc6c498fbb86dc1.png
[20210708205718601.png]: /images/20221005/d7b109daf63a47cebce98b6645dc1a9c.png
[20210708210116213.png]: /images/20221005/aac47d7b06be46b7a1f4fc2d27d37948.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaG1vbmtleQ_size_16_color_FFFFFF_t_70]: /images/20221005/5a6816d4eb434395be6f92d06d7ccfc0.png
[20210708210349924.png]: /images/20221005/149dc83cf73d4e908e9ffa210a733115.png
[20210708210607599.png]: /images/20221005/ceea23fb5e2c4ec4bb683c2c775e1e7a.png