jsondiffpatch

What is jsondiffpatch?

The jsondiffpatch npm package is a tool for computing the difference between two JSON objects and applying those differences to other JSON objects. It is useful for tasks such as data synchronization, version control, and change tracking in JSON data structures.

What are jsondiffpatch's main functionalities?

Diff

This feature computes the difference between two JSON objects. In this example, the difference between the 'left' and 'right' objects is calculated, resulting in a delta that shows the change in the 'age' property.

const jsondiffpatch = require('jsondiffpatch');
const left = { name: 'John', age: 30 };
const right = { name: 'John', age: 31 };
const delta = jsondiffpatch.diff(left, right);
console.log(delta);

Patch

This feature applies a delta (difference) to a JSON object to produce a new JSON object. In this example, the delta is applied to the 'left' object, resulting in the 'right' object with the updated 'age' property.

const jsondiffpatch = require('jsondiffpatch');
const left = { name: 'John', age: 30 };
const delta = { age: [30, 31] };
const right = jsondiffpatch.patch(left, delta);
console.log(right);

Unpatch

This feature reverts a JSON object to its previous state by applying the inverse of a delta. In this example, the delta is used to revert the 'right' object back to the 'left' object.

const jsondiffpatch = require('jsondiffpatch');
const right = { name: 'John', age: 31 };
const delta = { age: [30, 31] };
const left = jsondiffpatch.unpatch(right, delta);
console.log(left);

Reverse

This feature computes the inverse of a delta, which can be used to revert changes. In this example, the inverse of the delta is calculated, which can then be used to revert the changes made by the original delta.

const jsondiffpatch = require('jsondiffpatch');
const delta = { age: [30, 31] };
const reverseDelta = jsondiffpatch.reverse(delta);
console.log(reverseDelta);

Other packages similar to jsondiffpatch

deep-diff

The deep-diff package provides similar functionality for computing differences between JavaScript objects. It offers a more granular approach to detecting changes, including additions, deletions, and modifications. However, it does not provide built-in patching and unpatching capabilities like jsondiffpatch.

diff

The diff package is a general-purpose text and data comparison tool that can be used to compute differences between strings, arrays, and objects. While it is versatile and widely used, it lacks the specialized JSON diffing and patching features provided by jsondiffpatch.

fast-json-patch

The fast-json-patch package focuses on applying JSON Patch operations as defined by RFC 6902. It is optimized for performance and provides a simple API for applying and validating JSON patches. However, it does not compute differences between JSON objects, which is a key feature of jsondiffpatch.

README

jsondiffpatch

Diff & patch JavaScript objects

Live Demo

• min+gzipped ~ 16KB
• browser and server (/dist folder with bundles for UMD, commonjs, or ES modules)
• (optionally) uses google-diff-match-patch for long text diffs (diff at character level)
• 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
• reverse a delta
• unpatch (eg. revert object to its original state using a delta)
• simplistic, pure JSON, low footprint delta format
• multiple output formatters:
  • html (check it at the Live Demo)
  • annotated json (html), makes the JSON delta format self-explained
  • 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 modern browser and IE8+

And you can test your current browser visiting the test page.

• Node.js v4.8+

Usage

    // sample data
    var country = {
        name: "Argentina",
        capital: "Buenos Aires",
        independence: new Date(1816, 6, 9),
        unasur: true
    };

    // clone country, using dateReviver for Date objects
    var country2 = JSON.parse(JSON.stringify(country), jsondiffpatch.dateReviver);

    // make some changes
    country2.name = "Republica Argentina";
    country2.population = 41324992;
    delete country2.capital;

    var delta = jsondiffpatch.diff(country, country2);

    assertSame(delta, {
        "name":["Argentina","Republica Argentina"], // old value, new value
        "population":["41324992"], // new value
        "capital":["Buenos Aires", 0, 0] // deleted
    });

    // patch original
    jsondiffpatch.patch(country, delta);

    // reverse diff
    var reverseDelta = jsondiffpatch.reverse(delta);
    // also country2 can be return to original value with: jsondiffpatch.unpatch(country2, delta);

    var delta2 = jsondiffpatch.diff(country, country2);
    assert(delta2 === undefined)
    // undefined => no difference

Array diffing:

    // sample data
    var country = {
        name: "Argentina",
        cities: [
        {
            name: 'Buenos Aires',
            population: 13028000,
        },
        {
            name: 'Cordoba',
            population: 1430023,
        },
        {
            name: 'Rosario',
            population: 1136286,
        },
        {
            name: 'Mendoza',
            population: 901126,
        },
        {
            name: 'San Miguel de Tucuman',
            population: 800000,
        }
        ]
    };

    // clone country
    var country2 = JSON.parse(JSON.stringify(country));

    // delete Cordoba
    country.cities.splice(1, 1);

    // add La Plata
    country.cities.splice(4, 0, {
        name: 'La Plata'
        });

    // modify Rosario, and move it
    var rosario = country.cities.splice(1, 1)[0];
    rosario.population += 1234;
    country.cities.push(rosario);

    // create a configured instance, match objects by name
    var diffpatcher = jsondiffpatch.create({
        objectHash: function(obj) {
            return obj.name;
        }
    });

    var delta = diffpatcher.diff(country, country2);

    assertSame(delta, {
        "cities": {
            "_t": "a", // indicates this node is an array (not an object)
            "1": [
                // inserted at index 1
                {
                    "name": "Cordoba",
                    "population": 1430023
                }]
            ,
            "2": {
                // population modified at index 2 (Rosario)
                "population": [
                    1137520,
                    1136286
                ]
            },
            "_3": [
                // removed from index 3
                {
                    "name": "La Plata"
                }, 0, 0],
            "_4": [
                // move from index 4 to index 2
                '', 2, 3]
        }
    });

For more example cases (nested objects or arrays, long text diffs) check 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

npm install jsondiffpatch

var jsondiffpatch = require('jsondiffpatch').create(options);

browser

In a browser, you could load directly a bundle in /dist, eg. /dist/jsondiffpatch.umd.js.

Options

var jsondiffpatch = require('jsondiffpatch').create({
    // used to match objects when diffing arrays, by default only === operator is used
    objectHash: function(obj) {
        // this function is used only to when objects are not equal by ref
        return obj._id || obj.id;
    },
    arrays: {
        // default true, detect items moved inside the array (otherwise they will be registered as remove+add)
        detectMove: true,
        // default false, the value of items moved is not included in deltas
        includeValueOnMove: false
    },
    textDiff: {
        // default 60, minimum string length (left and right sides) to use text diff algorythm: google-diff-match-patch
        minLength: 60
    },
    propertyFilter: function(name, context) {
      /*
       this optional function can be specified to ignore object properties (eg. volatile data)
        name: property name, present in either context.left or context.right objects
        context: the diff context (has context.left and context.right objects)
      */
      return name.slice(0, 1) !== '$';
    },
    cloneDiffValues: false /* default false. if true, values in the obtained delta will be cloned
      (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.
      instead of true, a function can be specified here to provide a custom clone(value)
      */
});

Visual Diff

<!DOCTYPE html>
<html>
    <head>
        <script type="text/javascript" src="public/build/jsondiffpatch.min.js"></script>
        <script type="text/javascript" src="public/build/jsondiffpatch-formatters.min.js"></script>
        <link rel="stylesheet" href="public/formatters-styles/html.css" type="text/css" />
        <link rel="stylesheet" href="public/formatters-styles/annotated.css" type="text/css" />
    </head>
    <body>
        <div id="visual"></div>
        <hr/>
        <div id="annotated"></div>
        <script>
            var left = { a: 3, b: 4 };
            var right = { a: 5, c: 9 };
            var delta = jsondiffpatch.diff(left, right);

            // beautiful html diff
            document.getElementById('visual').innerHTML = jsondiffpatch.formatters.html.format(delta, left);

            // self-explained json
            document.getElementById('annotated').innerHTML = jsondiffpatch.formatters.annotated.format(delta, left);
        </script>
    </body>
</html>

To see formatters in action check the Live Demo.

For more details check Formatters documentation

Console

# diff two json files, colored output (using chalk lib)
./node_modules/.bin/jsondiffpatch ./left.json ./right.json

# or install globally
npm install -g jsondiffpatch

jsondiffpatch ./demo/left.json ./demo/right.json

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.