Introduction to JS variables and their scope knowledge points

1. Variables and their scope: Variables are divided into "global variables" and "local variables". "Global variables" are declared outside the function and can be used by all functions, while "local variables" are declared inside the function body and can only be used in Used within the function body in which the variable is defined.
(Note: There is no var keyword when declaring variables, but directly assigned variables are global variables)

2. In the function body, local variables have higher priority than global variables.

According to my understanding, the final output answer of the above example should be: 1 2 2 1; but the correct answer is: undefined 2 2 1; The reason is that the same name is declared both outside and inside the function body variables, local variables override global variables.
3. How to read the local variables inside the function body from the outside?
Generally speaking, only external global variables can be directly obtained from inside the function body, but local variables inside the function body cannot be obtained from the outside. However, this can be achieved by defining another function inside the function body to return local variables, and then calling the function from the outside.