Diferencia entre var, const y let
Var : crea variables de forma global por defecto
let : crea variables según el contexto o scope donde este
const : crea variables valores constantes que no se pueden modificar
var is a variable that can be inherited to its descendant scopes.
let acts as a variable in its block where it was defined and cannot be inherited to other scopes.
const is a variable that cannot be reassigned more than once.