jsondiffpatch

jsondiffpatch.com
Diff & patch JavaScript objects

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Live Demo

• min+gzipped ~ 16KB
• browser and server (ESM-only)
• deep diff, use delta to patch
• smart array diffing using LCS, IMPORTANT NOTE: to match objects inside an array you must provide an objectHash function (this is how objects are matched, otherwise a dumb match by position is used). For more details, check Array diff documentation
• (optionally) text diffing of long strings powered by google-diff-match-patch (diff at character level)
• reverse a delta, unpatch (eg. revert object to its original state using a delta)
• multiple output formats:
  • pure JSON, low footprint delta format
  • visual diff (html), see demo
  • annotated JSON (html), to help explain the delta format with annotations
  • JSON Patch (RFC 6902), can generate patches, and also apply them
  • console (colored), try running ./node_modules/.bin/jsondiffpatch left.json right.json
  • write your own! check Formatters documentation
• BONUS: jsondiffpatch.clone(obj) (deep clone)

Supported platforms

• Any browser that supports ES6
• Node.js 18, 20+

Usage

on your terminal:

1npx jsondiffpatch --help

or as a library:

1// sample data
2const country = {
3  name: 'Argentina',
4  capital: 'Buenos Aires',
5  independence: new Date(1816, 6, 9),
6};
7
8// clone country, using dateReviver for Date objects
9const country2 = JSON.parse(JSON.stringify(country), jsondiffpatch.dateReviver);
10
11// make some changes
12country2.name = 'Republica Argentina';
13country2.population = 41324992;
14delete country2.capital;
15
16const delta = jsondiffpatch.diff(country, country2);
17
18assertSame(delta, {
19  name: ['Argentina', 'Republica Argentina'], // old value, new value
20  population: ['41324992'], // new value
21  capital: ['Buenos Aires', 0, 0], // deleted
22});
23
24// patch original
25jsondiffpatch.patch(country, delta);
26
27// reverse diff
28const reverseDelta = jsondiffpatch.reverse(delta);
29// also country2 can be return to original value with: jsondiffpatch.unpatch(country2, delta);
30
31const delta2 = jsondiffpatch.diff(country, country2);
32assert(delta2 === undefined);
33// undefined => no difference

Array diffing:

1// sample data
2const country = {
3  name: 'Argentina',
4  cities: [
5    {
6      name: 'Buenos Aires',
7      population: 13028000,
8    },
9    {
10      name: 'Cordoba',
11      population: 1430023,
12    },
13    {
14      name: 'Rosario',
15      population: 1136286,
16    },
17    {
18      name: 'Mendoza',
19      population: 901126,
20    },
21    {
22      name: 'San Miguel de Tucuman',
23      population: 800000,
24    },
25  ],
26};
27
28// clone country
29const country2 = JSON.parse(JSON.stringify(country));
30
31// delete Cordoba
32country.cities.splice(1, 1);
33
34// add La Plata
35country.cities.splice(4, 0, {
36  name: 'La Plata',
37});
38
39// modify Rosario, and move it
40const rosario = country.cities.splice(1, 1)[0];
41rosario.population += 1234;
42country.cities.push(rosario);
43
44// create a configured instance, match objects by name
45const diffpatcher = jsondiffpatch.create({
46  objectHash: function (obj) {
47    return obj.name;
48  },
49});
50
51const delta = diffpatcher.diff(country, country2);
52
53assertSame(delta, {
54  cities: {
55    _t: 'a', // indicates this node is an array (not an object)
56    1: [
57      // inserted at index 1
58      {
59        name: 'Cordoba',
60        population: 1430023,
61      },
62    ],
63    2: {
64      // population modified at index 2 (Rosario)
65      population: [1137520, 1136286],
66    },
67    _3: [
68      // removed from index 3
69      {
70        name: 'La Plata',
71      },
72      0,
73      0,
74    ],
75    _4: [
76      // move from index 4 to index 2
77      '',
78      2,
79      3,
80    ],
81  },
82});

For more example cases (nested objects or arrays, long text diffs) check packages/jsondiffpatch/test/examples/

If you want to understand deltas, see delta format documentation

Installing

NPM

This works for node, or in browsers if you already do bundling on your app

1npm install jsondiffpatch

1import {* as jsondiffpatch} from 'jsondiffpatch';
2const jsondiffpatchInstance = jsondiffpatch.create(options);

browser

In a browser, you can load a bundle using a tool like esm.sh or Skypack.

Options

1import * as jsondiffpatch from 'jsondiffpatch';
2
3// Only import if you want text diffs using diff-match-patch
4import { diff_match_patch } from '@dmsnell/diff-match-patch';
5
6const jsondiffpatchInstance = jsondiffpatch.create({
7  // used to match objects when diffing arrays, by default only === operator is used
8  objectHash: function (obj) {
9    // this function is used only to when objects are not equal by ref
10    return obj._id || obj.id;
11  },
12  arrays: {
13    // default true, detect items moved inside the array (otherwise they will be registered as remove+add)
14    detectMove: true,
15    // default false, the value of items moved is not included in deltas
16    includeValueOnMove: false,
17  },
18  textDiff: {
19    // If using text diffs, it's required to pass in the diff-match-patch library in through this proprty.
20    // Alternatively, you can import jsondiffpatch using `jsondiffpatch/with-text-diffs` to avoid having to pass in diff-match-patch through the options.
21    diffMatchPatch: diff_match_patch,
22    // default 60, minimum string length (left and right sides) to use text diff algorithm: google-diff-match-patch
23    minLength: 60,
24  },
25  propertyFilter: function (name, context) {
26    /*
27       this optional function can be specified to ignore object properties (eg. volatile data)
28        name: property name, present in either context.left or context.right objects
29        context: the diff context (has context.left and context.right objects)
30      */
31    return name.slice(0, 1) !== '$';
32  },
33  cloneDiffValues: false /* default false. if true, values in the obtained delta will be cloned
34      (using jsondiffpatch.clone by default), to ensure delta keeps no references to left or right objects. this becomes useful if you're diffing and patching the same objects multiple times without serializing deltas.
35      instead of true, a function can be specified here to provide a custom clone(value).
36      */
37  omitRemovedValues: false /* if you don't need to unpatch (reverse deltas),
38      "old"/"left" values (removed or replaced) are not included in the delta.
39      you can set this to true to get more compact deltas.
40      */,
41});

Visual Diff

1<!doctype html>
2<html>
3  <head>
4    <link rel="stylesheet" href="./style.css" type="text/css" />
5    <link
6      rel="stylesheet"
7      href="https://esm.sh/jsondiffpatch@0.6.0/lib/formatters/styles/html.css"
8      type="text/css"
9    />
10    <link
11      rel="stylesheet"
12      href="https://esm.sh/jsondiffpatch@0.6.0/lib/formatters/styles/annotated.css"
13      type="text/css"
14    />
15  </head>
16  <body>
17    <div id="visual"></div>
18    <hr />
19    <div id="annotated"></div>
20    <script type="module">
21      import * as jsondiffpatch from 'https://esm.sh/jsondiffpatch@0.6.0';
22      import * as annotatedFormatter from 'https://esm.sh/jsondiffpatch@0.6.0/formatters/annotated';
23      import * as htmlFormatter from 'https://esm.sh/jsondiffpatch@0.6.0/formatters/html';
24
25      const left = { a: 3, b: 4 };
26      const right = { a: 5, c: 9 };
27      const delta = jsondiffpatch.diff(left, right);
28
29      // beautiful html diff
30      document.getElementById('visual').innerHTML = htmlFormatter.format(
31        delta,
32        left,
33      );
34
35      // self-explained json
36      document.getElementById('annotated').innerHTML =
37        annotatedFormatter.format(delta, left);
38    </script>
39  </body>
40</html>

To see formatters in action check the Live Demo.

For more details check Formatters documentation

Plugins

diff(), patch() and reverse() functions are implemented using Pipes & Filters pattern, making it extremely customizable by adding or replacing filters on a pipe.

Check Plugins documentation for details.

Related Projects

• jsondiffpatch.net (C#)
• SystemTextJson.JsonDiffPatch (C#)
• Go JSON Diff (and Patch)
• json-diff-patch (python)
• jsondiffpatch-react, also check docs for usage in react

All contributors ✨