JS advanced - lexical scope

Scope classification ：
1. Static scope （ Lexical scope ）：Javascript
2. Dynamic scope ：bash
Characteristic contrast ：
1. The lexical scope is determined when the code is defined , Instead of looking at the call
2. Dynamic scope is determined during code execution

 var a = 10;
 function fun（）{
    
      console.log（a）;
};
 function fun2（）{
    
      var a = 20;
      fun（）;
};
 fun2（）;// Output 10
 fun（）;// Output 10

Because of the function fun and fun2 Are defined in the global environment , So their upper scope is the global scope Global, and Global It holds variables a=10, So when fun（） Calls and fun2（） When calling , Look for yourself first , If you can't find it, go to the overall situation ！ So they all output 10, That is to say, the lexical scope has been determined when the code is defined , Instead of looking at function calls