JS function and variable have the same name (function and variable parsing rules)

Log in and copy

       

        console.log(a)
        
　　var a = 3
        
　　function a(){}
       
       

        
1.
        
2.
        
3.
       

Print ：ƒ a() {}

analysis ：

1、 The function declaration will be at the top , Variable declarations will be at the top ,​ Function declarations are more important than variable declarations ​

2、 Variable declaration and assignment are written together （var）,js When parsing, the engine will split it into two parts: Declaration and assignment , The statement tops , The resolution remains in its original position （ This only refers to var The way ,let and const Has block level scope , And the declared variables are not mounted to window On ）

3、 Declared variables will not be declared repeatedly

The above expression is equivalent to ：

Log in and copy

       

        function a() {}
        
      var a
        
      console.log(a)
        
      a = 3
       
       

        
1.
        
2.
        
3.
        
4.