In JavaScript, variable and functions are hoisted. Let's TAKE FUNCTION hoisting FIRST. Basically, the JavaScript interpreter looks ahead to find all variable declarations and then hoists them to the top of the function where they're declared. For example:

 FOO(); // Here foo is still undefined 

 var foo = function foo()
{ 
return 12; 
 }; 

Behind the scene of the code above looks LIKE this:

var foo = undefined;

foo(); // Here foo is undefined 

foo = function foo()
{
/ Some code stuff
}
var foo = undefined;
foo = function foo()
{
/ Some code stuff
}
foo(); // Now foo is defined here.

In JavaScript, variable and functions are hoisted. Let's take function hoisting first. Basically, the JavaScript interpreter looks ahead to find all variable declarations and then hoists them to the top of the function where they're declared. For example:

 foo(); // Here foo is still undefined 

 var foo = function foo()
{ 
return 12; 
 }; 

Behind the scene of the code above looks like this:

var foo = undefined;

foo(); // Here foo is undefined 

foo = function foo()
{
/ Some code stuff
}
var foo = undefined;
foo = function foo()
{
/ Some code stuff
}
foo(); // Now foo is defined here.