Xdiff NPM | npm.io

xdiff

diff, diff3, patch (nearly) arbitary json documents.

examples

var x = require('xdiff')

var a = SOMEOBJECT
var b = SOMEOBJECT_AFTER_CHANGES

var diff = x.diff(a, b)

// can apply a diff to A to get B

var patched = x.patch(a, diff)

require('assert').deepEqual(a, patched)

diff, patch, diff3

with diff you can create a diff that is applyable with patch you can diff nested objects, and arrays.

with diff3 you create a diff from two objects that have been edited concurrently, you need to also to pass the concestor.

also see adiff which xdiff depends on to diff arrays.

xdiff is compatible with snob

Objects

var a = {a: true, c: 'deleteme'}
var b = {a: true, b: false}
var p = x.diff(a, b)

will create a diff like this:

[ ['set', ['root', 'b'], false]
, ['del', ['root', 'c']] ]

operations on nested objects are represented by thier path, unless the object has an ID. (see below)

var a0 = {A: {AA: '?'}}
var a1 = {A: {AA: 'aardvark'}}
var p = x.diff(a, b)

will create diff like this:

 [['set', ['root', 'A', 'AA'], 'aardvark']]

Arrays

var a = [1, 2 , 3]
var b = [0, 1, 'hello', 3]
var p = x.diff(a, b)

will create a diff like

[ 'splice', ['root'], [
    [ 1, 1, 'hello] //at index 1 delete one item and insert hello
  , [ 0, 0, 0]      //at index 0 delete 0 items and insert `0`
]

Objects in Arrays

if you give objects an ID, then xdiff will beable to track it properly, even if it's moved. even if it's concurrently changed.

var a = [{__id__: '#1'}, 5, {__id__: '#2'}]
var b = [5, {__id__: '#2'}, {__id__: '#1', prop: 'surprise'}]
var p = x.diff(a, b)

will produce a diff like this

  [ ['set', ['#1', 'prop'], 'surprise'] //this applies the change to object #1
  , ['splice', ['root'], [ 
      [ 3, 0, '#=*#1'] //this just updates the reference!
    , [ 0, 1]
    ] ]
  ]

if you don't don't use id's xdiff won't know that an object that has changed is actually the same object. this would cause it to reinsert a new copy of that object.

id's are this is really useful when you need to do 3-way-merges to merge together concurrent changes.

in a future version, xdiff will allow changing the id key. currently it uses only the __id__ property.