Variable declartion is used to indicate that a variable exists, independently of giving it a value. This would typically reserve space for the variable handle itself (either within static space or as part of a stack frame) and could presumably also claim some dynamic memory (though that seems more typically to be part of initialization).
The original and least restrictive form of variable declartion is
using the var statement:
var <name>;This would typically be done as part of initializing the value,
though some practices may prefer “hoisting” the declarations to the top
of the binding environment to clarify the actual execution flow (in
light of possibly ascending through environments). I believe
var has some scoping differences when compared to newer
alternatives, but within my personal taste any of those are likely to be
idiosyncracies that are best avoided (and var also would be
avoided for the more expressive newer alternatives.