diffList( oldList, newList, [identity] )

Compares two lists and produces a sequence of patches that can be applied to make oldList take the shape of newList.

var diffList = require("can-diff/list/list");

console.log(diff([1], [1, 2])); // -> [{type: "splice", index: 1, deleteCount: 0, insert: [2]}]
console.log(diff([1, 2], [1])); // -> [{type: "splice", index: 1, deleteCount: 1, insert: []}]

// with an optional identity function:
diffList(
    [{id:1},{id:2}],
    [{id:1},{id:3}],
    (a,b) => a.id === b.id
); // -> [{type: "splice", index: 1, deleteCount: 1, insert: [{id:3}]}]

The patch algorithm is linear with respect to the length of the lists and therefore does not produce a perfect edit distance (which would be at least quadratic).

It is designed to work with most common list change scenarios, when items are inserted or removed to a list (as opposed to moved with in the last).

For example, it is able to produce the following patches:

diffList(
    ["a","b","c","d"],
    ["a","b","X","Y","c","d"]
); // -> [{type: "splice", index: 2, deleteCount: 0, insert: ["X","Y"]}]