In the same scope,
var
and non-
var
declared variable won't make any difference. A variable is the "container for an object". As soon as you assign some different object to a variable (it could be the object of different type), you loose the access to the old object, unless it was preserved somewhere else.
The cases where
var
makes some difference are explained here:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/var[
^].
The difference is made when you use the same variable name in outer scope and, below its declaration, in sub-scope. Then the same name could be interpreted as the same variable as it was in the outer scope, or (with "var") — a reintroduced one, unrelated to the first one.
—SA