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https://github.com/rgrove/parse-xml

A fast, safe, compliant XML parser for Node.js and browsers.
https://github.com/rgrove/parse-xml

javascript js node nodejs parse-xml parser parsing typescript xml xml-parser xml-parsing

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A fast, safe, compliant XML parser for Node.js and browsers.

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# parse-xml

A fast, safe, compliant XML parser for Node.js and browsers.

[![npm version](https://badge.fury.io/js/%40rgrove%2Fparse-xml.svg)](https://badge.fury.io/js/%40rgrove%2Fparse-xml) [![Bundle size](https://badgen.net/bundlephobia/minzip/@rgrove/parse-xml)](https://bundlephobia.com/result?p=@rgrove/parse-xml) [![CI](https://github.com/rgrove/parse-xml/actions/workflows/ci.yml/badge.svg)](https://github.com/rgrove/parse-xml/actions/workflows/ci.yml)

## Links

- [API Docs](https://rgrove.github.io/parse-xml/)
- [GitHub](https://github.com/rgrove/parse-xml)
- [npm](https://www.npmjs.com/package/@rgrove/parse-xml)

## Installation

```
npm install @rgrove/parse-xml
```

Or, if you like living dangerously, you can load [the minified bundle](https://unpkg.com/@rgrove/parse-xml/dist/global.min.js) in a browser via [Unpkg](https://unpkg.com/) and use the `parseXml` global.

## Features

- Returns a convenient [object tree](#basic-usage) representing an XML document.

- Works great in Node.js and browsers.

- Provides [helpful, detailed error messages](#friendly-errors) with context when a document is not well-formed.

- Mostly conforms to [XML 1.0 (Fifth Edition)](https://www.w3.org/TR/2008/REC-xml-20081126/) as a non-validating parser (see [below](#not-features) for details).

- Passes all relevant tests in the [XML Conformance Test Suite](https://www.w3.org/XML/Test/).

- Written in TypeScript and compiled to ES2020 JavaScript for Node.js and ES2017 JavaScript for browsers. The browser build is also optimized for minification.

- Extremely [fast](#benchmark) and surprisingly [small](https://bundlephobia.com/result?p=@rgrove/parse-xml).

- Zero dependencies.

## Not Features

While this parser is capable of parsing document type declarations (``) and including them in the node tree, it doesn't actually do anything with them. External document type definitions won't be loaded, and the parser won't validate the document against a DTD or resolve custom entity references defined in a DTD.

In addition, the only supported character encoding is UTF-8 because it's not feasible (or useful) to support other character encodings in JavaScript.

## Examples

### Basic Usage

**ESM**

```js
import { parseXml } from '@rgrove/parse-xml';
parseXml('I like fuzzy kittens.');
```

**CommonJS**

```js
const { parseXml } = require('@rgrove/parse-xml');
parseXml('I like fuzzy kittens.');
```

The result is an [`XmlDocument`](https://rgrove.github.io/parse-xml/classes/XmlDocument.html) instance containing the parsed document, with a structure that looks like this (some properties and methods are excluded for clarity; see the [API docs](https://rgrove.github.io/parse-xml/) for details):

```js
{
type: 'document',
children: [
{
type: 'element',
name: 'kittens',
attributes: {
fuzzy: 'yes'
},
children: [
{
type: 'text',
text: 'I like fuzzy kittens.'
}
],
parent: { ... },
isRootNode: true
}
]
}
```

All parse-xml objects have `toJSON()` methods that return JSON-serializable objects, so you can easily convert an XML document to JSON:

```js
let json = JSON.stringify(parseXml(xml));
```

### Friendly Errors

When something goes wrong, parse-xml throws an error that tells you exactly what happened and shows you where the problem is so you can fix it.

```js
parseXml('baz');
```

**Output**

```
Error: Missing end tag for element bar (line 1, column 14)
baz
^
```

In addition to a helpful message, error objects have the following properties:

- **column** _Number_

Column where the error occurred (1-based).

- **excerpt** _String_

Excerpt from the input string that contains the problem.

- **line** _Number_

Line where the error occurred (1-based).

- **pos** _Number_

Character position where the error occurred relative to the beginning of the input (0-based).

## Why another XML parser?

There are many XML parsers for Node, and some of them are good. However, most of them suffer from one or more of the following shortcomings:

- Native dependencies.

- Loose, non-standard parsing behavior that can lead to unexpected or even unsafe results when given input the author didn't anticipate.

- Kitchen sink APIs that tightly couple a parser with DOM manipulation functions, a stringifier, or other tooling that isn't directly related to parsing and consuming XML.

- Stream-based parsing. This is great in the rare case that you need to parse truly enormous documents, but can be a pain to work with when all you want is a node tree.

- Poor error handling.

- Too big or too Node-specific to work well in browsers.

parse-xml's goal is to be a small, fast, safe, compliant, non-streaming, non-validating, browser-friendly parser, because I think this is an under-served niche.

I think parse-xml demonstrates that it's not necessary to jettison the spec entirely or to write complex code in order to implement a small, fast XML parser.

Also, it was fun.

## Benchmark

Here's how parse-xml's performance stacks up against a few comparable libraries:

- [fast-xml-parser](https://github.com/NaturalIntelligence/fast-xml-parser), which claims to be the fastest pure JavaScript XML parser
- [libxmljs2](https://github.com/marudor/libxmljs2), which is based on the native libxml library written in C
- [xmldoc](https://github.com/nfarina/xmldoc), which is based on [sax-js](https://github.com/isaacs/sax-js)

While libxmljs2 is faster at parsing medium and large documents, its performance comes at the expense of a large C dependency, no browser support, and a [history of security vulnerabilities](https://www.cvedetails.com/vulnerability-list/vendor_id-1962/product_id-3311/Xmlsoft-Libxml2.html) in the underlying libxml2 library.

In these results, "ops/s" refers to operations per second. Higher is faster.

```
Node.js v18.14.0 / Darwin arm64
Apple M1 Max

Running "Small document (291 bytes)" suite...
Progress: 100%

@rgrove/parse-xml 4.1.0:
191 553 ops/s, ±0.10% | fastest

fast-xml-parser 4.1.1:
142 565 ops/s, ±0.11% | 25.57% slower

libxmljs2 0.31.0 (native):
74 646 ops/s, ±0.30% | 61.03% slower

xmldoc 1.2.0 (sax-js):
66 823 ops/s, ±0.09% | slowest, 65.12% slower

Finished 4 cases!
Fastest: @rgrove/parse-xml 4.1.0
Slowest: xmldoc 1.2.0 (sax-js)

Running "Medium document (72081 bytes)" suite...
Progress: 100%

@rgrove/parse-xml 4.1.0:
1 065 ops/s, ±0.11% | 49.81% slower

fast-xml-parser 4.1.1:
637 ops/s, ±0.12% | 69.98% slower

libxmljs2 0.31.0 (native):
2 122 ops/s, ±2.48% | fastest

xmldoc 1.2.0 (sax-js):
444 ops/s, ±0.36% | slowest, 79.08% slower

Finished 4 cases!
Fastest: libxmljs2 0.31.0 (native)
Slowest: xmldoc 1.2.0 (sax-js)

Running "Large document (1162464 bytes)" suite...
Progress: 100%

@rgrove/parse-xml 4.1.0:
93 ops/s, ±0.10% | 53.27% slower

fast-xml-parser 4.1.1:
48 ops/s, ±0.60% | 75.88% slower

libxmljs2 0.31.0 (native):
199 ops/s, ±1.47% | fastest

xmldoc 1.2.0 (sax-js):
38 ops/s, ±0.09% | slowest, 80.9% slower

Finished 4 cases!
Fastest: libxmljs2 0.31.0 (native)
Slowest: xmldoc 1.2.0 (sax-js)
```

See the [parse-xml-benchmark](https://github.com/rgrove/parse-xml-benchmark) repo for instructions on how to run this benchmark yourself.

## License

[ISC License](LICENSE)