Javascript function scoping and hoisting

Question

I just read a great article about JavaScript Scoping and Hoisting by Ben Cherry in which he gives the following example:

var a = 1;

function b() {
    a =          


        

Answer 1

scpope & closure & hoisting (var/function)

1. scpope : the global var can be access in any place(the whole file scope), local var only can be accessed by the local scope(function/block scope)!
   Note: if a local variable not using var keywords in a function, it will become a global variable!
2. closure : a function inner the other function, which can access local scope(parent function) & global scope, howerver it's vars can't be accessed by others! unless, your return it as return value!
3. hoisting : move all declare/undeclare vars/function to the scope top, than assign the value or null!
   Note: it just move the declare,not move the value!

var a = 1;                
//"a" is global scope
function b() {  
   var a = function () {}; 
   //"a" is local scope 
   var x = 12; 
   //"x" is local scope 
   a = 10;
   //global variable "a" was overwrited by the local variable "a"  
   console.log("local a =" + a);
   return console.log("local x = " + x);
}       
b();
// local a =10
// local x = 12
console.log("global a = " + a);
// global a = 1
console.log("can't access local x = \n");
// can't access local x = 
console.log(x);
// ReferenceError: x is not defined