Javascript scope chain generation Sequence

I have recently seen some ideas.

Javascript scope chain sometimes causes some strange problems. As a weak type of JavaScript, functions are also objects. The scope of variables is effective in the function body and has no block scope.

When JavaScript looks for variables or objects, it first looks for the internal context of the function body, and then the external context of the function.

While Javascript is in the lexical scope when constructing the scope, not when executing it. See the example of Abruzzi:

 
VaR STR = "Global"; function scopetest () {print (STR); var STR = "local"; print (STR) ;} scopetest ();
 

Result:

 
Undefined
Local
 

The parser does not call the external str of JavaScript. After the syntax analysis, it constructs the scope. At this time, the str in the scopetest () function is initialized in the entire function, and no value is assigned, therefore, execute print to output undefined.

Make a small modification and define STR in scopetest as a global variable. The result is easy to understand.

VaRStr= "Global";
FunctionScopetest (){
Print (STR );
Str= "Local";//STR is a global variable.
Print (STR );
}
Scopetest ();
 

The result is

    global  
  Local 
 is actually the relationship between global variables and the scope of local variables, javascript has no block scope, which affects the scope of local variables, resulting in some special situations. 
 I do not know whether the understanding is reasonable. Please advise. 
 A lot of unreasonable points. I feel more reasonable about the resolution here. reply on the 12th floor.