README
parse-xml
A fast, safe, compliant XML parser for Node.js and browsers.
Contents
Installation
npm install @rgrove/parse-xml
Or, if you like living dangerously, you can load the minified UMD bundle
in a browser via Unpkg and use the parseXml global.
Features
Returns an object tree representing an XML document.
Works great in Node.js and in modern browsers.
Provides helpful, detailed error messages with context when a document is not well-formed.
Mostly conforms to XML 1.0 (Fifth Edition) as a non-validating parser (see below for details).
Passes all relevant tests in the XML Conformance Test Suite.
Not Features
This parser currently discards document type declarations (<!DOCTYPE ... >)
and all their contents, because they're rarely useful and some of their features
aren't safe when the XML being parsed comes from an untrusted source.
In addition, the only supported character encoding is UTF-8 because it's not feasible (or useful) to suppport other character encodings in JavaScript.
API
See API.md for complete API docs.
Examples
Basic Usage
const parseXml = require('@rgrove/parse-xml');
let doc = parseXml('<kittens fuzzy="yes">I like fuzzy kittens.</kittens>');
The result is an XmlDocument instance containing the parsed document, with a
structure that looks like this (some properties and methods are excluded for
clarity; see the API docs for details):
{
type: 'document',
children: [
{
type: 'element',
name: 'kittens',
attributes: {
fuzzy: 'yes'
},
children: [
{
type: 'text',
text: 'I like fuzzy kittens.'
}
],
parent: { ... },
isRootNode: true
}
]
}
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.
parseXml('<foo><bar>baz</foo>');
Output
Error: Missing end tag for element bar (line 1, column 14)
<foo><bar>baz</foo>
^
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 stacks up against two comparable libraries, libxmljs2 (which is based on the native libxml library) and xmldoc (which is based on sax-js).
Node.js v14.15.4 / Darwin x64
Intel(R) Core(TM) i7-6920HQ CPU @ 2.90GHz
Running "Small document (291 bytes)" suite...
Progress: 100%
@rgrove/parse-xml 3.0.0:
77 109 ops/s, ±0.46% | fastest
libxmljs2 0.26.6 (native):
29 480 ops/s, ±4.62% | slowest, 61.77% slower
xmldoc 1.1.2 (sax-js):
36 035 ops/s, ±0.62% | 53.27% slower
Finished 3 cases!
Fastest: @rgrove/parse-xml 3.0.0
Slowest: libxmljs2 0.26.6 (native)
Running "Medium document (72081 bytes)" suite...
Progress: 100%
@rgrove/parse-xml 3.0.0:
321 ops/s, ±0.99% | 54.34% slower
libxmljs2 0.26.6 (native):
703 ops/s, ±10.64% | fastest
xmldoc 1.1.2 (sax-js):
235 ops/s, ±0.50% | slowest, 66.57% slower
Finished 3 cases!
Fastest: libxmljs2 0.26.6 (native)
Slowest: xmldoc 1.1.2 (sax-js)
Running "Large document (1162464 bytes)" suite...
Progress: 100%
@rgrove/parse-xml 3.0.0:
20 ops/s, ±0.48% | 72.97% slower
libxmljs2 0.26.6 (native):
74 ops/s, ±12.02% | fastest
xmldoc 1.1.2 (sax-js):
19 ops/s, ±1.68% | slowest, 74.32% slower
Finished 3 cases!
Fastest: libxmljs2 0.26.6 (native)
Slowest: xmldoc 1.1.2 (sax-js)
See the parse-xml-benchmark repo for instructions on running this benchmark yourself.