json-diff

What is json-diff?

The json-diff npm package is a tool for comparing JSON objects and generating a diff between them. It is useful for identifying changes between two JSON structures, which can be helpful in various scenarios such as configuration management, data synchronization, and debugging.

What are json-diff's main functionalities?

Generate Diff

This feature allows you to generate a diff between two JSON objects. The code sample demonstrates how to use the json-diff package to compare two JSON objects and print the differences.

const jsonDiff = require('json-diff');
const oldJson = { name: 'Alice', age: 25 };
const newJson = { name: 'Alice', age: 26 };
const diff = jsonDiff.diffString(oldJson, newJson);
console.log(diff);

Pretty Print Diff

This feature allows you to generate a color-coded diff for better readability. The code sample shows how to enable color in the diff output.

const jsonDiff = require('json-diff');
const oldJson = { name: 'Alice', age: 25 };
const newJson = { name: 'Alice', age: 26 };
const diff = jsonDiff.diffString(oldJson, newJson, { color: true });
console.log(diff);

Compare JSON Files

This feature allows you to compare JSON data from files. The code sample demonstrates how to read JSON data from two files and generate a diff.

const fs = require('fs');
const jsonDiff = require('json-diff');
const oldJson = JSON.parse(fs.readFileSync('old.json', 'utf8'));
const newJson = JSON.parse(fs.readFileSync('new.json', 'utf8'));
const diff = jsonDiff.diffString(oldJson, newJson);
console.log(diff);

Other packages similar to json-diff

deep-diff

The deep-diff package provides a way to find differences between two JavaScript objects. It supports nested structures and can generate detailed diffs. Compared to json-diff, deep-diff offers more granular control over the diffing process and can be used for more complex data structures.

diff

The diff package is a general-purpose text diffing library that can be used to compare JSON strings. While it is not specifically designed for JSON, it can be used to generate diffs for any text data. It offers a variety of diffing algorithms and options for customization.

jsondiffpatch

The jsondiffpatch package is designed specifically for comparing JSON objects and generating patches. It supports complex data structures and can generate both diffs and patches that can be applied to update JSON objects. It offers more advanced features compared to json-diff, such as patch generation and application.

README

JSON structural diff

Does exactly what you think it does:

Installation

npm install json-diff

Usage

Simple:

json-diff a.json b.json

Detailed:

% json-diff --help
Usage: json-diff [-vjC] first.json second.json

Arguments:
  first.json            Old file
  second.json           New file

General options:
  -v, --verbose         Output progress info
  -C, --[no-]color      Colored output
  -j, --raw-json        Display raw JSON encoding of the diff
  -h, --help            Display this usage information

Features

• colorized, diff-like output
• fuzzy matching of modified array elements (when array elements are object hierarchies)
• reasonable test coverage (far from 100%, though)

Tests

Run:

`npm test`

Output:

colorize
  ✓ should return ' <value>' for a scalar value
  ✓ should return '-<old value>', '+<new value>' for a scalar diff
  ✓ should return '-<removed key>: <removed value>' for an object diff with a removed key
  ✓ should return '+<added key>: <added value>' for an object diff with an added key
  ✓ should return '+<added key>: <added stringified value>' for an object diff with an added key and a non-scalar value
  ✓ should return ' <modified key>: <colorized diff>' for an object diff with a modified key
  ✓ should return '+<inserted item>' for an array diff
  ✓ should return '-<deleted item>' for an array diff

diff
  with simple scalar values
    ✓ should return undefined for two identical numbers
    ✓ should return undefined for two identical strings
    ✓ should return { __old: <old value>, __new: <new value> } object for two different numbers
  with objects
    ✓ should return undefined for two objects with identical contents
    ✓ should return undefined for two object hierarchies with identical contents
    ✓ should return { <key>__deleted: <old value> } when the second object is missing a key
    ✓ should return { <key>__added: <new value> } when the first object is missing a key
    ✓ should return { <key>: { __old: <old value>, __new: <new value> } } for two objects with diffent scalar values for a key
    ✓ should return { <key>: <diff> } with a recursive diff for two objects with diffent values for a key
  with arrays of scalars
    ✓ should return undefined for two arrays with identical contents
    ✓ should return [..., ['-', <removed item>], ...] for two arrays when the second array is missing a value
    ✓ should return [..., ['+', <added item>], ...] for two arrays when the second one has an extra value
    ✓ should return [..., ['+', <added item>]] for two arrays when the second one has an extra value at the end (edge case test)
  with arrays of objects
    ✓ should return undefined for two arrays with identical contents
    ✓ should return [..., ['-', <removed item>], ...] for two arrays when the second array is missing a value
    ✓ should return [..., ['+', <added item>], ...] for two arrays when the second array has an extra value
    ✓ should return [..., ['~', <diff>], ...] for two arrays when an item has been modified (note: involves a crazy heuristic)

✔ 25 tests complete (12ms)

License

© Andrey Tarantsov. Distributed under the MIT license.