fauxdom

FauxDOM

A fast and lightweight JavaScript library for parsing, modifying, and outputting HTML using a (mostly) standard DOM API, either on the server in Node.js or in any reasonably modern browser.

Description

FauxDOM is meant to parse HTML the same way browsers do, while also being as fast as possible. Some compromises were made for performance reasons that make FauxDOM treat some less-than-valid HTML different from a standards-compliant browser. With this in mind, any major structural differences between what FauxDOM produces and what a browser produces should be safe to view as a problem with the HTML document itself. However, if you come across a scenario where you believe FauxDOM is incorrect, and this same issue hasn't been reported yet, feel free to open a new issue.

Having a mostly standards-compliant DOM API means that some parts of FauxDOM's implementation of the standards fully work, while others either don't or are different in some regard. The documentation will list properties and methods as either standard, semi-standard (when their behaviour is different from the standard), or non-standard to give you a more clear idea of how FauxDOM differs from the standard DOM API.

What Works

• Standards-based API

  FauxDOM implements a subset of the standard DOM API as defined by the WHATWG, and documented by MDN.

  The full list of supported API methods and properties can be found in the documentation.

• Selector engine

  The main portion of the Selectors Level 4 API that can be used to identify elements has been implemented and is used by Node.closest(), Node.matches(), Node.querySelector(), and Node.querySelectorAll().

  The full list of supported selectors can be found in the selectors documentation.

What Doesn't

• Namespaces

  HTML namespaces in general are not supported by FauxDOM. Any standard DOM API methods that end in "NS" are not implemented, and any other methods that should work with namespaces according to the spec will simply ignore any requests to work on namespaces.

  Namespaces in selectors (for Node.querySelector(), etc.), in addition to not being supported, will actually cause a syntax error to be thrown.

• Attribute nodes

  While FauxDOM fully supports attributes on elements, attribute values are only ever worked with as strings rather than attribute node objects. As such, any standard DOM API methods that work with attribute nodes (eg. createAttribute(), getAttributeNode(), setAttributeNode(), etc.) are not implemented.

• Element adoption

  For performance reasons, FauxDOM doesn't implement what the WHATWG's HTML 5 spec calls the adoption agency algorithm, instead opting for a significantly more simplistic method of determining which elements can be the children of which other elements when parsing HTML.

What's Different

• Array-like objects

  For many standard DOM API methods that would normally work with a collection of values using an Array-like object (such as NamedNodeMap and NodeList), FauxDOM instead simply uses an Array to store the values. The main exception to this is DOMTokenList, accessible from Node.classList, which is a mostly complete implementation of the standard DOM API class of the same name.

Installing

Server-side (Node.js)

npm install fauxdom

Client-side (browsers)

For client-side use, FauxDOM comes in two distinct flavours:

1. fauxdom.zip — Old-school everything-lives-in-the-global-scope style

   Including this in your page will result in a single class called DOM being globally defined.

2. fauxdom.module.zip — Way-of-the-future ES module style

   The module exports a single class named DOM.

Download the latest release in the style you want.

entities.zip and entities.module.zip are also available to download if you want to be able to encode and decode the entire set of HTML entities as defined by the HTML 5 standard. Please see the note about the standard set of entities if you intend to use the full set.

Using

In Node.js, as is usual, you'll need to require() FauxDOM to use it:

const DOM = require( "fauxdom" );

For use on a webpage, include fauxdom.js before code that uses FauxDOM:

<script src="fauxdom.js" type="text/javascript"></script>
<script>var doc = new DOM();</script>

FauxDOM can also be used as an ES module by importing the module's single export DOM:

import DOM from "/fauxdom.js";

Once the DOM class is accessible by your code, you're ready to start creating and working with documents. The DOM reference documentation is an excellent place to start reading about how to use FauxDOM.

Examples

As a simple example of making an empty document be slightly more meaningful, the following code:

const document = new DOM( "<!DOCTYPE html><html><head></head><body></body></html>" );

document.title = "Page";

const header = document.createElement( "h1" );
header.textContent = "Hello, world.";
document.body.appendChild( header );

console.log( document.innerHTML );

will output (with whitespace added for readability):

<!DOCTYPE html>
<html>
    <head>
        <title>Page</title>
    </head>
    <body>
        <h1>Hello, world.</h1>
    </body>
</html>

A more advanced use-case could be to create a Node.js server that implements a JavaScript-based system similar to PHP:

const html = "<?js '<div>'+ (21 * 2) +'</div>'?>";
const document = new DOM( html, {allowProcessingInstructions: true} );

document.forEach( node =>
{
    if ( node.target === "js" )
        node.outerHTML = eval( node.textContent );
}, DOM.Node.PROCESSING_INSTRUCTION_NODE );

console.log( document.innerHTML );

Even though the above code isn't anywhere near production quality, with absolutely no error handling or considerations for security, it is the minimum amount of work needed to allow the example code above to output:

<div>42</div>

Requirements

FauxDOM requires at least Node.js 6 (or compatible) on the server side, and Chrome 5, Firefox 4, Internet Explorer 9, Opera 11.6, or Safari 5 (or compatible) on the client side. These browser requirements are driven by the need for Object.defineProperties, for which no valid polyfill exists (getters and setters are needed, but not supported in versions of IE less than 9).

FauxDOM also requires, and includes, basic polyfills for the following JavaScript APIs. The first version of each browser that supports each API is also listed.

	Chrome	Edge	Firefox	IE	Opera	Safari
Symbol	38	12	36	none	25	9
Object.assign	45	12	34	none	32	9
Object.freeze	6	12	4	9	12	5.1
Object.hasOwn	93	93	92	none	79	15.4
String.fromCodePoint	41	12	29	none	28	10
String.prototype.trimEnd	66	79	61	none	53	12
String.prototype.trimStart	66	79	61	none	53	12
Array.prototype.find	45	12	25	none	32	8
Function.prototype.bind	7	12	4	9	11.6	5.1

If your project already includes a polyfill for any of the above, include your polyfill before FauxDOM to keep FauxDOM's simplistic polyfills from being used.

License

MIT