# htmlparser2

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The fast & forgiving HTML/XML parser.

_htmlparser2 is [the fastest HTML parser](#performance), and takes some shortcuts to get there. If you need strict HTML spec compliance, have a look at [parse5](https://github.com/inikulin/parse5)._

## Installation

    npm install htmlparser2

A live demo of `htmlparser2` is available [on AST Explorer](https://astexplorer.net/#/2AmVrGuGVJ).

## Ecosystem

| Name                                                          | Description                                             |
| ------------------------------------------------------------- | ------------------------------------------------------- |
| [htmlparser2](https://github.com/fb55/htmlparser2)            | Fast & forgiving HTML/XML parser                        |
| [domhandler](https://github.com/fb55/domhandler)              | Handler for htmlparser2 that turns documents into a DOM |
| [domutils](https://github.com/fb55/domutils)                  | Utilities for working with domhandler's DOM             |
| [css-select](https://github.com/fb55/css-select)              | CSS selector engine, compatible with domhandler's DOM   |
| [cheerio](https://github.com/cheeriojs/cheerio)               | The jQuery API for domhandler's DOM                     |
| [dom-serializer](https://github.com/cheeriojs/dom-serializer) | Serializer for domhandler's DOM                         |

## Usage

`htmlparser2` itself provides a callback interface that allows consumption of documents with minimal allocations.
For a more ergonomic experience, read [Getting a DOM](#getting-a-dom) below.

```js
import * as htmlparser2 from "htmlparser2";

const parser = new htmlparser2.Parser({
    onopentag(name, attributes) {
        /*
         * This fires when a new tag is opened.
         *
         * If you don't need an aggregated `attributes` object,
         * have a look at the `onopentagname` and `onattribute` events.
         */
        if (name === "script" && attributes.type === "text/javascript") {
            console.log("JS! Hooray!");
        }
    },
    ontext(text) {
        /*
         * Fires whenever a section of text was processed.
         *
         * Note that this can fire at any point within text and you might
         * have to stitch together multiple pieces.
         */
        console.log("-->", text);
    },
    onclosetag(tagname) {
        /*
         * Fires when a tag is closed.
         *
         * You can rely on this event only firing when you have received an
         * equivalent opening tag before. Closing tags without corresponding
         * opening tags will be ignored.
         */
        if (tagname === "script") {
            console.log("That's it?!");
        }
    },
});
parser.write(
    "Xyz <script type='text/javascript'>const foo = '<<bar>>';</script>"
);
parser.end();
```

Output (with multiple text events combined):

```
--> Xyz
JS! Hooray!
--> const foo = '<<bar>>';
That's it?!
```

This example only shows three of the possible events.
Read more about the parser, its events and options in the [wiki](https://github.com/fb55/htmlparser2/wiki/Parser-options).

### Usage with streams

While the `Parser` interface closely resembles Node.js streams, it's not a 100% match.
Use the `WritableStream` interface to process a streaming input:

```js
import { WritableStream } from "htmlparser2/lib/WritableStream";

const parserStream = new WritableStream({
    ontext(text) {
        console.log("Streaming:", text);
    },
});

const htmlStream = fs.createReadStream("./my-file.html");
htmlStream.pipe(parserStream).on("finish", () => console.log("done"));
```

## Getting a DOM

The `DomHandler` produces a DOM (document object model) that can be manipulated using the [`DomUtils`](https://github.com/fb55/DomUtils) helper.

```js
import * as htmlparser2 from "htmlparser2";

const dom = htmlparser2.parseDocument(htmlString);
```

The `DomHandler`, while still bundled with this module, was moved to its [own module](https://github.com/fb55/domhandler).
Have a look at that for further information.

## Parsing Feeds

`htmlparser2` makes it easy to parse RSS, RDF and Atom feeds, by providing a `parseFeed` method:

```javascript
const feed = htmlparser2.parseFeed(content, options);
```

## Performance

After having some artificial benchmarks for some time, **@AndreasMadsen** published his [`htmlparser-benchmark`](https://github.com/AndreasMadsen/htmlparser-benchmark), which benchmarks HTML parses based on real-world websites.

At the time of writing, the latest versions of all supported parsers show the following performance characteristics on GitHub Actions (sourced from [here](https://github.com/AndreasMadsen/htmlparser-benchmark/blob/e78cd8fc6c2adac08deedd4f274c33537451186b/stats.txt)):

```
htmlparser2        : 2.17215 ms/file ± 3.81587
node-html-parser   : 2.35983 ms/file ± 1.54487
html5parser        : 2.43468 ms/file ± 2.81501
neutron-html5parser: 2.61356 ms/file ± 1.70324
htmlparser2-dom    : 3.09034 ms/file ± 4.77033
html-dom-parser    : 3.56804 ms/file ± 5.15621
libxmljs           : 4.07490 ms/file ± 2.99869
htmljs-parser      : 6.15812 ms/file ± 7.52497
parse5             : 9.70406 ms/file ± 6.74872
htmlparser         : 15.0596 ms/file ± 89.0826
html-parser        : 28.6282 ms/file ± 22.6652
saxes              : 45.7921 ms/file ± 128.691
html5              : 120.844 ms/file ± 153.944
```

## How does this module differ from [node-htmlparser](https://github.com/tautologistics/node-htmlparser)?

In 2011, this module started as a fork of the `htmlparser` module.
`htmlparser2` was rewritten multiple times and, while it maintains an API that's mostly compatible with `htmlparser`, the projects don't share any code anymore.

The parser now provides a callback interface inspired by [sax.js](https://github.com/isaacs/sax-js) (originally targeted at [readabilitySAX](https://github.com/fb55/readabilitysax)).
As a result, old handlers won't work anymore.

The `DefaultHandler` was renamed to clarify its purpose (to `DomHandler`). The old name is still available when requiring `htmlparser2` and your code should work as expected.

The `RssHandler` was replaced with a `getFeed` function that takes a `DomHandler` DOM and returns a feed object. There is a `parseFeed` helper function that can be used to parse a feed from a string.

## Security contact information

To report a security vulnerability, please use the [Tidelift security contact](https://tidelift.com/security).
Tidelift will coordinate the fix and disclosure.

## `htmlparser2` for enterprise

Available as part of the Tidelift Subscription.

The maintainers of `htmlparser2` and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications. Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use. [Learn more.](https://tidelift.com/subscription/pkg/npm-htmlparser2?utm_source=npm-htmlparser2&utm_medium=referral&utm_campaign=enterprise&utm_term=repo)
