Discussion on the scope of Javascript variables

Variable scope problems in Js :

1. No block-level scope. Variables in Js are not scoped with {}, unlike C/C++/Java.

Such as:

 if(true){

     var name = "qqyumidi";

 }

             

 alert(name);  //  Results: qqyumidi

Js adds variables defined in if to the current execution environment, especially when using for loops.

 for(var i=0; i<10; i++){

     ;

 }

 

 alert(i);   //  Results: 10 

Here is only personal understanding, if there is a mistake, please let us know.