Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. It includes many web standards from WHATWG DOM and HTML.
The goal of Happy DOM is to emulate enough of a web browser to be useful for testing, scraping web sites and server-side rendering.
Happy DOM focuses heavily on performance and can be used as an alternative to JSDOM.
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Custom Elements (Web Components)
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Shadow Root (Shadow DOM)
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Declarative Shadow DOM
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Mutation Observer
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Tree Walker
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Fetch
And much more..
npm install happy-dom
Happy DOM can be used as a simulated Browser or by using the Window class directly to quickly setup up a DOM.
import { Window } from 'happy-dom';
const window = new Window({ url: 'https://localhost:8080' });
const document = window.document;
document.body.innerHTML = '<div class="container"></div>';
const container = document.querySelector('.container');
const button = document.createElement('button');
container.appendChild(button);
// Outputs "<div class="container"><button></button></div>"
console.log(document.body.innerHTML);
import { Browser, BrowserErrorCaptureEnum } from 'happy-dom';
const browser = new Browser({ settings: { errorCapture: BrowserErrorCaptureEnum.processLevel } });
const page = browser.newPage();
// Navigates page
await page.goto('https://github.com/capricorn86');
// Clicks on link
page.mainFrame.document.querySelector('a[href*="capricorn86/happy-dom"]').click();
// Waits for all operations on the page to complete (fetch, timers etc.)
await page.waitUntilComplete();
// Outputs "GitHub - capricorn86/happy-dom: Happy DOM..."
console.log(page.mainFrame.document.title);
// Closes the browser
await browser.close();
Read more about how to use Happy DOM in our Wiki.
Operation | JSDOM | Happy DOM |
---|---|---|
Import / Require | 333 ms | 45 ms |
Parse HTML | 256 ms | 26 ms |
Serialize HTML | 65 ms | 8 ms |
Render custom element | 214 ms | 19 ms |
querySelectorAll('tagname') | 4.9 ms | 0.7 ms |
querySelectorAll('.class') | 6.4 ms | 3.7 ms |
querySelectorAll('[attribute]') | 4.0 ms | 1.7 ms |
querySelectorAll('[class~="name"]') | 5.5 ms | 2.9 ms |
querySelectorAll(':nth-child(2n+1)') | 10.4 ms | 3.8 ms |
See how the test was done here
Happy DOM provide with a package called @happy-dom/jest-environment that makes it possible to use Happy DOM with Jest.
Vitest supports Happy DOM out of the box.
Happy DOM provide with a package called @happy-dom/global-registrator that can register Happy DOM globally. It makes it possible to use Happy DOM for testing in a Node environment.