microdiff

What is microdiff?

The microdiff npm package is a lightweight utility for calculating the differences between two JavaScript objects. It is designed to be fast and efficient, making it suitable for applications where performance is critical.

What are microdiff's main functionalities?

Basic Object Diffing

This feature allows you to find the differences between two simple objects. The code sample demonstrates how to use microdiff to compare two objects and log the differences.

const diff = require('microdiff');
const obj1 = { a: 1, b: 2 };
const obj2 = { a: 1, b: 3 };
const differences = diff(obj1, obj2);
console.log(differences);

Nested Object Diffing

This feature allows you to find differences in nested objects. The code sample shows how microdiff can be used to compare nested objects and identify changes at any level of depth.

const diff = require('microdiff');
const obj1 = { a: 1, b: { c: 2, d: 3 } };
const obj2 = { a: 1, b: { c: 2, d: 4 } };
const differences = diff(obj1, obj2);
console.log(differences);

Array Diffing

This feature allows you to find differences between arrays. The code sample demonstrates how microdiff can be used to compare two arrays and log the differences.

const diff = require('microdiff');
const arr1 = [1, 2, 3];
const arr2 = [1, 2, 4];
const differences = diff(arr1, arr2);
console.log(differences);

Other packages similar to microdiff

deep-diff

The deep-diff package provides similar functionality to microdiff, allowing you to find differences between two JavaScript objects. It supports nested objects and arrays, but it is generally larger and may not be as performant as microdiff.

diff

The diff package is a more general-purpose diffing library that can be used to find differences between strings, arrays, and objects. It is more feature-rich than microdiff but also larger and potentially slower for object diffing.

just-diff

The just-diff package is another lightweight library for diffing JavaScript objects. It is similar in size and performance to microdiff, but it may have a different API and feature set.

README

Microdiff is a tiny (<1kb), fast, zero dependency object and array comparison library. It is significantly faster than most other deep comparison libraries, and has full TypeScript support.

💡 I recommend reading this blog post:

Building the fastest object and array differ for an explanation of how Microdiff achieves its size and speed.

Features

• 🚀 More than double the speed of other object diff libraries
• 📦 Extremely lightweight, <1kb minified
• 🌎 Supports Deno, Node, Bun, the web, and even service workers. Also comes with built-in Typescript types
• 🔰 Very easy to use, having just a single diff() function
• 📅 Full support for objects like new Date() and new RegExp()

Get started

First, install Microdiff

npm i microdiff

If you are using Deno, you can import it from Deno.land with the link https://deno.land/x/microdiff@VERSION/index.ts (remember to change @VERSION to the version you want to use).

After you install it, import it and run it on two objects.

import diff from "microdiff";

const obj1 = {
	originalProperty: true,
};
const obj2 = {
	originalProperty: true,
	newProperty: "new",
};

console.log(diff(obj1, obj2));
// [{type: "CREATE", path: ["newProperty"], value: "new"}]

If you are using CommonJS, you can import it like this:

const diff = require("microdiff").default;

There are three different types of changes: CREATE, REMOVE, and CHANGE. The path property gives a path to the property in the new object (or the old object in the case of REMOVE). Each element in the paths is a key to the next property a level deeper until you get to the property changed, and it is a string or a number, depending on whether the object is an Array or Object (Objects with number keys will still be strings). The value property exists in types CREATE and CHANGE, and it contains the value of the property added/changed/deleted. The oldValue property exists in the type CHANGE and REMOVE, and it contains the old value of the property.

Cycles support

By default, Microdiff supports cyclical references, but if you are sure that the object has no cycles like parsed JSON, you can disable cycles using the cyclesFix option.

diff(obj1, obj2, { cyclesFix: false });

Benchmarks

Geometric mean of time per operation relative to Microdiff (no cycles) (100%==equal time, lower is better)
microdiff (no cycles): 100%
microdiff: 149%
deep-diff: 197%
deep-object-diff: 288%
jsDiff: 1565%

These results are from a suite of benchmarks matching real world use cases of multiple open-source repos using various diffing algorithm, running under Node 22.12.0 on a Ryzen 7950x clocked at ~4.30 GHz. The benchmarks are run through mitata to minimize random variation and time most accurately. You can view the full benchmark code in bench.js and the benchmarks themselves at benchmarks/applied.

Of course, these benchmarks should be taken with a grain of salt due to the inherent errors present in benchmarking JavaScript, but if you want to run them on your own computer in your own runtime/setup, run bench.js.

Contributing

Thanks for helping the project out! Contributing is pretty simple. Fork the repository (if you need more information on how to do this, check out this GitHub guide), clone it to your computer, and start programming! To compile the program, run npm run build (replace npm with pnpm or yarn if you are using one of those). This will create CommonJS and ESM modules in /dist.

To benchmark microdiff, you can run npm run bench. This will automatically build Microdiff and run a benchmarking program comparing microdiff to other common diffing libraries.

Finally, Microdiff has an extensive test suite which you should take advantage of. To make sure everything is working correctly, you can run npm run test. npm run test builds the project and then runs the entire test suite on the new version. If you are fixing a bug, be sure to add a test for that. Also, make sure you read the Code of Conduct before contributing.