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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.

DOM Features

• Custom Elements (Web Components)
• Declarative Shadow DOM
• Mutation Observer
• Tree Walker
• Fetch API
• File Reader
• CSS Style Declaration
• Form Data
• Selection
• Form Validity State
• IFrames
• Cookies
• Clipboard
• ECMAScript Modules (e.g. import and export)

And much more..

Browser Features

• Browser API
• Virtual Console
• Wait Until Complete
• Wait For Navigation

Other Features

• Server-Side Rendering

Performance

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(':nth-child(2n+1)')	10.4 ms	3.8 ms

See how the test was done here