Redeclaring a javascript variable

Question

In this tutorial there is written:

If you redeclare a JavaScript variable, it will not lose its value.

Why should I redeclare a variable? Is it

Answer 1

It doesn't lose it's value because of Hoisting

var x = 5;
var x;

// this is same as

var x; // undefined;
x = 5;

So when you say "If you redeclare a JavaScript variable, it will not lose its value."

As per hoisting, the declaration(s), all of them , move to the top. And then the variable is assigned.

var x = 25;
var x; // redeclare first time
var x; // redeclare second time

// is same as 

var x; // undefined
var x; // Not sure if this happens, but doesn't make a difference, it's still undefined
x = 25;

As for practicality, it happens sometimes. Look at @steveoliver 's answer.