#array-diff Find diffs of arrays in javascript based on longest common subsequences.

var diff = require('array-diff')({compress: true})
var before =  [1, 2, 3, 4, 5]
var after =   [1, 2, 3, 4, 7, 5]
var result = diffCompressed(before, after)
// returns:
[['=', [1, 2, 3, 4]], ['+', [7]], ['=', [5]]]

If you have arrays of unique elements you can diff re-orders. 'x' denotes a "cut" and 'p' a "paste":

var diff = require('array-diff')({unique: true, compress: true})
var before =  [1, 2, 3, 4, 5, 6]
var after =   [1, 2, 3, 6, 4, 5]
var result = diff(before)
// returns:
[['=', [1, 2, 3]], ['p', [6]], ['=', [4, 5]], ['x', [6]]]

This library is used by array-merge to do 3-way merges.