This tool merges two lists, removing duplicates, and doing everything possible to maintain the order of the two lists.
This tool guarantees that the order of the first list is preserved (that is, if x comes before y in the first list, x comes before y in the returned list) and tries not to undo the order of the second list, though sometimes it is unavoidable.
For example, if we have
list1 = [1, 2, 4] and
list2 = [2, 1, 3, 4], then the
merged list would be
[1, 2, 3, 4], since that preserves the order of
while doing the best job possible of preserving the order of
A case like
list1 = [1, 3],
list2 = [3, 2, 1] is more complicated. It's not
clear what the best merged list is, but it's probably either
[2, 1, 3] or
[1, 3, 2].
In general, it's not totally clear what the "best" merged list is, but there are some basic properties that anyone would expect:
- Since the order of list1 is preserved, the merged list will look like the first list with the elements exclusive to the second inserted in betweeen
list2[i]is not in
list1, and it is possible to insert
list1without contradicting the order of
list2, then it should be inserted in such a way
This tool is very slow, crossing the 100ms mark with lists around 150 in length,
and growing at a rate of
O(list2.length*list2.length*(list1.length + list2.length)) from there.
Installation / Usage
npm install combine-lists
Use like so:
var combineLists = require('combine-lists'); combineLists([1, 2], [2, 3]); // [1, 2, 3]