JSON Diff Kit

A better JSON differ & viewer library written in TypeScript. Try it out in the playground!

Install

You can install json-diff-kit via various package managers.

# using npm
npm i json-diff-kit --save

# using yarn
yarn add json-diff-kit

# using pnpm
pnpm add json-diff-kit

Quick Start

To generate the diff data:

import { Differ } from 'json-diff-kit';
// or if you are using vue, you can import the differ only
import Differ from 'json-diff-kit/dist/differ';

// the two JS objects
const before = {
  a: 1,
  b: 2,
  d: [1, 5, 4],
  e: ['1', 2, { f: 3, g: null, h: [5], i: [] }, 9],
  m: [],
  q: 'JSON diff can\'t be possible',
  r: 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.',
  s: 1024,
};
const after = {
  b: 2,
  c: 3,
  d: [1, 3, 4, 6],
  e: ['1', 2, 3, { f: 4, g: false, i: [7, 8] }, 10],
  j: { k: 11, l: 12 },
  m: [
    { n: 1, o: 2 },
    { p: 3 },
  ],
  q: 'JSON diff is possible!',
  r: 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed quasi architecto beatae incididunt ut labore et dolore magna aliqua.',
  s: '1024',
};

// all configs are optional
const differ = new Differ({
  detectCircular: true,    // default `true`
  maxDepth: Infinity,      // default `Infinity`
  showModifications: true, // default `true`
  arrayDiffMethod: 'lcs',  // default `"normal"`, but `"lcs"` may be more useful
});

// you may want to use `useMemo` (for React) or `computed` (for Vue)
// to avoid redundant computations
const diff = differ.diff(before, after);
console.log(diff);

You can use your own component to visualize the diff data, or use the built-in viewer:

import { Viewer } from 'json-diff-kit';
import type { DiffResult } from 'json-diff-kit';

import 'json-diff-kit/dist/viewer.css';

interface PageProps {
  diff: [DiffResult[], DiffResult[]];
}

const Page: React.FC<PageProps> = props => {
  return (
    <Viewer
      diff={props.diff}          // required
      indent={4}                 // default `2`
      lineNumbers={true}         // default `false`
      highlightInlineDiff={true} // default `false`
      inlineDiffOptions={{
        mode: 'word',            // default `"char"`, but `"word"` may be more useful
        wordSeparator: ' ',      // default `""`, but `" "` is more useful for sentences
      }}
    />
  );
};

The result is here:

More Complex Usages

Please check the playground page, where you can adjust nearly all parameters and see the result.

CLI Tool

You can use the CLI tool to generate the diff data from two JSON files. Please install the package terminal-kit before using it.

pnpm add terminal-kit # or make sure it's already installed in your project

# Compare two JSON files, output the diff data to the terminal.
# You can navigate it using keyboard like `less`.
jsondiff run path/to/before.json path/to/after.json

# Output the diff data to a file.
# Notice there will be no side-by-side view since it's not a TTY.
jsondiff run path/to/before.json path/to/after.json -o path/to/result.diff

# Use a custom configuration file and output the diff data to a file.
jsondiff run path/to/before.json path/to/after.json -c path/to/config.json -o path/to/result.diff

# Print the help message.
jsondiff --help
jsondiff run --help

Algorithm Details

Please refer to the article JSON Diff Kit: A Combination of Several Simple Algorithms.

Features & Roadmap

• [x] Provide a Differ class and a Viewer component
• [x] Merge "remove & add" at the same place as a modification
• [x] Support inline diffing by word instead of by character
• [x] Generate code directly in the demo page (covered by playground)
• [x] Optimise Viewer performance by adding virtual scrolling
• [x] Add CLI tool
• [ ] Improve unit tests
• [ ] Provide a Vue version of Viewer

License

MIT