---

[![Build Status][build-badge]][build]
[![Code Coverage][coverage-badge]][coverage]
[![version][version-badge]][package]
[![downloads][downloads-badge]][npmtrends]
[![MIT License][license-badge]][license]
[![All Contributors][all-contributors-badge]](#contributors-)
[![PRs Welcome][prs-badge]][prs]
[![Code of Conduct][coc-badge]][coc]

> WARNING: Please _only_ use this if you really can't find a way to use
> React.useEffect. There's often a better way to do what you're trying to do
> than a deep comparison.

The Problem

React's built-in [useEffect][react-hooks] hook has a second argument called
the "dependencies array" and it allows you to optimize when React will call your
effect callback. React will do a comparison between each of the values (via
[Object.is][object-is]) to determine whether your effect callback should be
called.

The problem is that if you need to provide an object for one of those
dependencies and that object is new every render, then even if none of the
properties changed, your effect will get called anyway.

Table of Contents

- Installation
- Usage
- Other Solutions
- Issues
- 🐛 Bugs
- 💡 Feature Requests
- Contributors ✨
- LICENSE

Installation

This module is distributed via [npm][npm] which is bundled with [node][node] and
should be installed as one of your project's dependencies:

``shell
npm install --save use-deep-compare-effect
`

Usage

You use it in place of React.useEffect.

> NOTE: Only use this if your values are objects or arrays that contain objects.
> Otherwise, you should just use React.useEffect. In case of "polymorphic"
> values (eg: sometimes object, sometimes a boolean), use
> useDeepCompareEffectNoCheck, but do it at your own risk, as maybe there can
> be better approaches to the problem.

> NOTE: Be careful when your dependency is an object which contains function.
> If that function is defined on the object during a render, then it's changed
> and the effect callback will be called every render.
> Issue has more context.

Example:

`jsx
import React from 'react'
import ReactDOM from 'react-dom'
import useDeepCompareEffect from 'use-deep-compare-effect'

function Query({query, variables}) {
// some code...

useDeepCompareEffect(
() => {
// make an HTTP request or whatever with the query and variables
// optionally return a cleanup function if necessary
},
// query is a string, but variables is an object. With the way Query is used
// in the example above, variables will be a new object every render.
// useDeepCompareEffect will do a deep comparison and your callback is only
// run when the variables object actually has changes.
[query, variables],
)

return


}
``

Other Solutions

use-custom-compare-effect

Issues

_Looking to contribute? Look for the [Good First Issue][good-first-issue]
label._

$3

Please file an issue for bugs, missing documentation, or unexpected behavior.

[See Bugs][bugs]

$3

Please file an issue to suggest new features. Vote on feature requests by adding
a 👍. This helps maintainers prioritize what to work on.

[See Feature Requests][requests]

Contributors ✨

Thanks goes to these people ([emoji key][emojis]):

Kent C. Dodds 💻 📖 🚇 ⚠️	Edygar de Lima Oliveira 💻 ⚠️	Justin Dorfman 🔍	Anton Halim 📖	Michaël De Boey 💻	Tobias Büschel 📖	Peter Hozák 👀
Ricardo Busquet 👀	Dave Johansen 🐛	Sam Knutson 📖	Albert Lucianto 🐛 💻 ⚠️	Jasper Chang 📖	cvolant 💻

This project follows the [all-contributors][all-contributors] specification.
Contributions of any kind welcome!

LICENSE

MIT

[npm]: https://www.npmjs.com
[node]: https://nodejs.org
[build-badge]: https://img.shields.io/github/workflow/status/kentcdodds/use-deep-compare-effect/validate?logo=github&style=flat-square
[build]: https://github.com/kentcdodds/use-deep-compare-effect/actions?query=workflow%3Avalidate
[coverage-badge]: https://img.shields.io/codecov/c/github/kentcdodds/use-deep-compare-effect.svg?style=flat-square
[coverage]: https://codecov.io/github/kentcdodds/use-deep-compare-effect
[version-badge]: https://img.shields.io/npm/v/use-deep-compare-effect.svg?style=flat-square
[package]: https://www.npmjs.com/package/use-deep-compare-effect
[downloads-badge]: https://img.shields.io/npm/dm/use-deep-compare-effect.svg?style=flat-square
[npmtrends]: http://www.npmtrends.com/use-deep-compare-effect
[license-badge]: https://img.shields.io/npm/l/use-deep-compare-effect.svg?style=flat-square
[license]: https://github.com/kentcdodds/use-deep-compare-effect/blob/master/LICENSE
[prs-badge]: https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat-square
[prs]: http://makeapullrequest.com
[coc-badge]: https://img.shields.io/badge/code%20of-conduct-ff69b4.svg?style=flat-square
[coc]: https://github.com/kentcdodds/use-deep-compare-effect/blob/master/CODE_OF_CONDUCT.md
[emojis]: https://github.com/all-contributors/all-contributors#emoji-key
[all-contributors]: https://github.com/all-contributors/all-contributors
[all-contributors-badge]: https://img.shields.io/github/all-contributors/kentcdodds/use-deep-compare-effect?color=orange&style=flat-square
[bugs]: https://github.com/kentcdodds/use-deep-compare-effect/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+sort%3Acreated-desc+label%3Abug
[requests]: https://github.com/kentcdodds/use-deep-compare-effect/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc+label%3Aenhancement
[good-first-issue]: https://github.com/kentcdodds/use-deep-compare-effect/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc+label%3Aenhancement+label%3A%22good+first+issue%22
[react-hooks]: https://reactjs.org/docs/hooks-effect.html
[object-is]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is