What is parse5?
The parse5 npm package is a fast full-featured specification-compliant HTML parser for Node.js. It allows users to parse HTML documents and manipulate the resulting document tree structure. The package provides a variety of modules for parsing, serializing, and tree adaptation based on the DOM (Document Object Model) interface.
What are parse5's main functionalities?
Parsing HTML
This feature allows you to parse an HTML string into a document tree that can be manipulated or queried.
const parse5 = require('parse5');
const html = '<!DOCTYPE html><html><head></head><body>Hi there!</body></html>';
const document = parse5.parse(html);
Serializing Document
This feature enables you to serialize a document tree back into an HTML string.
const parse5 = require('parse5');
const document = parse5.parse('<!DOCTYPE html><html><head></head><body>Hi there!</body></html>');
const html = parse5.serialize(document);
Streaming
This feature allows you to use parse5 in a streaming mode, which is useful for processing large HTML documents without loading them entirely into memory.
const parse5 = require('parse5');
const fs = require('fs');
const file = fs.createReadStream('example.html');
const parser = new parse5.SAXParser();
parser.on('text', (text) => {
console.log(text);
});
file.pipe(parser);
Tree Adapters
This feature allows you to use different tree adapters to interact with the parsed document tree in a way that is compatible with other libraries or your own custom requirements.
const parse5 = require('parse5');
const htmlparser2Adapter = require('parse5-htmlparser2-tree-adapter');
const html = '<!DOCTYPE html><html><head></head><body>Hi there!</body></html>';
const document = parse5.parse(html, { treeAdapter: htmlparser2Adapter });
Other packages similar to parse5
cheerio
Cheerio is a fast, flexible, and lean implementation of core jQuery designed specifically for the server. It uses a very similar syntax to jQuery, allowing for manipulation of the elements in the parsed document tree. Cheerio is generally faster than parse5 for querying documents but does not strictly adhere to the HTML5 specification.
jsdom
jsdom is a pure-JavaScript implementation of many web standards, notably the WHATWG DOM and HTML Standards, for use with Node.js. It creates a DOM environment similar to that provided by web browsers, including a window object. jsdom is more feature-rich than parse5, providing a complete emulation of a web browser's environment, but it is also heavier and slower for simple parsing tasks.
htmlparser2
htmlparser2 is a forgiving HTML and XML parser. It is fast and has a simple API, but unlike parse5, it does not strictly adhere to the HTML5 parsing specification. It is suitable for parsing non-standard or malformed HTML.
parse5
Fast full-featured HTML parser for Node. Based on WHATWG HTML5 specification.
To build TestCafé we needed fast and ready for production HTML parser for node.js, which will parse HTML as a modern browser's parser.
Existing solutions were either too slow or their output was too inaccurate. So, this is how parse5 was born.
Install
$ npm install parse5
Usage and API
var Parser = require('parse5').Parser;
var parser = new Parser();
var document = parser.parse('<!DOCTYPE html><html><head></head><body>Hi there!</body></html>')
var fragment = parser.parseFragment('<title>Parse5 is fucking awesome!</title><h1>42</h1>');
Is it fast?
Check out this benchmark.
Starting benchmark. Fasten your seatbelts...
html5 (https://github.com/aredridel/html5) x 0.18 ops/sec ±5.92% (5 runs sampled)
htmlparser (https://github.com/tautologistics/node-htmlparser/) x 3.83 ops/sec ±42.43% (14 runs sampled)
htmlparser2 (https://github.com/fb55/htmlparser2) x 4.05 ops/sec ±39.27% (15 runs sampled)
parse5 (https://github.com/inikulin/parse5) x 3.04 ops/sec ±51.81% (13 runs sampled)
Fastest is htmlparser2 (https://github.com/fb55/htmlparser2),parse5 (https://github.com/inikulin/parse5)
So, parse5 is as fast as simple specification incompatible parsers and ~15-times(!) faster than the current specification compatible parser available for the node.
Testing
Test data is adopted from html5lib project. Parser is covered by more than 8000 test cases.
To run tests:
$ node test/run_tests.js
Custom tree adapter
You can create a custom tree adapter so parse5 can work with your own DOM-tree implementation.
Just pass your adapter implementation to the parser's constructor as an argument:
var Parser = require('parse5').Parser;
var myTreeAdapter = {
};
var parser = new Parser(myTreeAdapter);
Sample implementation can be found here.
The custom tree adapter should implement all methods exposed via exports
in the sample implementation.
Questions or suggestions?
If you have any questions, please feel free to create an issue here on github.
Author
Ivan Nikulin (ifaaan@gmail.com)