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<h1 align="center">jest-fixed-jsdom</h1> | ||
<p align="center">This library helps re-attach missing NodeJS globals definitions in JSDOM that Jest strips out</p> | ||
<p align="center">A superset of the JSDOM environment for Jest that respects Node.js globals.</p> | ||
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## Motivation | ||
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Jest strips out a number of NodeJS globals that are used in tests and libraries involving JSDOM, such as structuredClone, ReadableStream, and so on. This library patches these globals back in - there is no polyfilling or mocking involved, it simply re-attaches the missing globals to the JSDOM environment. If you've ever come across errors such as `ReferenceError: ReadableStream is not defined` or `ReferenceError: structuredClone is not defined`, this library is for you. If you were previously using (undici)[https://www.npmjs.com/package/undici] purely to solve this, you will no longer need it. | ||
When you use Jest with JSDOM you are getting a broken test environment. Some Node.js globals cease to exist (e.g. `Request`, `Response`, `TextEncoder`, `TextDecoder`, `ReadableStream`<sup><a href="https://github.com/mswjs/msw/issues/1916">1</a></sup>), while others stop behaving correctly (e.g. `Event`, `MessageEvent`<sup><a href="https://github.com/nodejs/undici/issues/2663">2</a></sup>, `structuredClone()`<sup><a href="https://github.com/mswjs/msw/issues/1931">3</a></sup>). That is caused by `jest-environment-jsdom` and JSDOM relying on polyfills to implement standard APIs that have been available globally both in the browser and in Node.js for years. | ||
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## Installation | ||
Here's a piece of valid JavaScript that works in both the browser and Node.js but fails in Jest/JSDOM: | ||
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`npm install jest-fixed-jsdom -D` | ||
```js | ||
new TextEncoder().encode('hello') | ||
``` | ||
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## Configuring your jest environment to use jest-fixed-jsdom | ||
``` | ||
ReferenceError: TextEncoder is not defined | ||
``` | ||
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You will need to add/modify two properties in your jest configuration to use jest-fixed-jsdom. | ||
**We strongly believe that a valid JavaScript code must compile regardless of what test environment you are using**. In fact, having a proper test environment is crucial to get any kind of value from your tests. Jest/JSDOM take that already working environment away from you. | ||
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```json | ||
{ | ||
"testEnvironment": "jest-fixed-jsdom" | ||
} | ||
We've built this project aims to fix that problem, restoring the global APIs that are present in both environments, providing better interoperability, stability, and consistent runtime behavior. | ||
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## Changes | ||
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This project "fixes" the following global APIs, overriding whichever polyfills they have with respective Node.js globals: | ||
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- `EventTarget` | ||
- `Event` | ||
- `MessageEvent` | ||
- `fetch()` | ||
- `Blob` | ||
- `FormData` | ||
- `Headers` | ||
- `Request` | ||
- `Response` | ||
- `ReadableStream` | ||
- `TextEncoder` | ||
- `TextDecoder` | ||
- `structuredClone()` | ||
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## Getting started | ||
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### Install | ||
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```sh | ||
npm i jest-fixed-jsdom --save-dev | ||
``` | ||
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Setting `testEnvironment` to `jest-fixed-jsdom` will tell Jest to use jest-fixed-jsdom as the test environment. Setting `customExportConditions` to an empty array will stop JSDOM from using the browser environment to load exports. | ||
### Configure Jest | ||
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In your `jest.config.js`, set the `testEnvironment` option to `jest-fixed-jsdom`: | ||
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```js | ||
// jest.config.js | ||
module.exports = { | ||
testEnvironment: 'jest-fixed-jsdom', | ||
} | ||
``` | ||
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> You can use any other `testEnvironmentOptions` you need. Those will be forwarded to the underlying `jest-environment-jsdom`. |