[SOLVED] How to work with copy of an array and reset it later

How to work with copy of an array and reset it later

I have an array list with all the predefined data I want to work on.

Then I want to make a copy of that array on which I do the work, i.e. shuffling and then popping one element. Now after the list is empty, I want to reset it, i.e. fill it again with the contents of list.

What I have now is this:

list = [{...}, {...}, {...}]
list2 = list

shuffle = (a) ->
  i = a.length
  while --i > 0
    j = ~~(Math.random() * (i + 1))
    t = a[j]
    a[j] = a[i]
    a[i] = t
  a

get_list_item = ->
  shuffle(list2)
  list2.pop()

reset_list = ->
  list2 = list

But after I've popped all the items from list2, reset_list() doesn't reset the list. It's still empty

Solution

list2 = list doesn't make a copy of list, it just creates another pointer to the same array. So when you are using pop() the original (and only) array loses elements.

Replace these instructions with list2 = list.slice 0 and it should work like you want it to.