aList.js

/*
Objects, as generic blobs of values, can be used to build all sorts of data
 structures. A common data structure is the list (not to be confused with the
  array). A list is a nested set of objects, with the first object holding a
   reference to the second, the second to the third, and so on.
   var list =
   { value : 1 ,
     rest : { value : 2 ,
       rest : { value : 3 ,
         rest : null } } };
The resulting objects form a chain, like this: A nice thing about lists is that
they can share parts of their structure. For example, if I create two new
values {value: 0, rest: list} and {value: -1, rest: list} (with list referring
to the variable defined earlier), they are both independent lists, but they
share the structure that makes up their last three elements. In addition,
the original list is also still a valid three-element list. Write a function
arrayToList that builds up a data structure like the previous one when given
[1, 2, 3] as argument, and write a listToArray function that produces an array
from a list. Also write the helper functions prepend , which takes an element
and a list and at the given position in the list, or undefined when there is no
such element. If you haven’t already, also write a recursive version of nth .
*/