Array add/remove item reminder

array add-remove

Summary:
--------
add:      unshift -> array <- push
remove:   shift   <- array -> pop

Chart:
------
          add  remove  start  end
   push    X                   X
    pop           X            X
unshift    X             X
  shift           X      X

array helpers

// removes item(s) from the original array
// returns an array of removed item(s)
function removeItem(array, item, itemAmount){
  var idx = array.indexOf(item);
  if(idx > -1) return array.splice(idx, itemAmount || 1);
}