easysax
v0.6.1
Published
pure javascript xml parser
Readme
EASYSAX - pure javascript sax-style parser for xml
Simple and fast SAX XML parser.
- Incremental processing: EasySAX supports incremental data processing. This allows parsing files several gigabytes in size with minimal RAM consumption, passing data to the parser as it is read.
- Namespaces: Supports namespace normalization.
- Fast: High-performance streaming engine.
The parser was written for the RSS reader http://zzreader.com (not working) Remains the fastest SAX XML parser for JS by 2026
Install
$ npm install easysaxBenchmark
sh: bun benchmark/stream.js
file: mock elems text
------------------------------------------------------------------------------------------
only load - total: 169.28 time: 2.51 500 MB
easysax ns=on uq=on attr=on - total: 3109.29 time: 2670.36 500 MB 7505704 5003804
easysax ns=off uq=on attr=on - total: 2482.34 time: 2100.68 500 MB 7505704 5003804
easysax ns=off uq=off attr=on - total: 1369.77 time: 1066.33 500 MB 7505704 5003804
easysax ns=off uq=off attr=off - total: 1237.50 time: 887.20 500 MB 7505704 5003804
eksml uq=off attr=on - total: 1557.89 time: 1259.11 500 MB 7505704 2501901
saxes uq=on attr=on - total: 7909.32 time: 7439.90 500 MB 7505704 5003804
ltx uq=on attr=on - total: 14608.25 time: 14167.45 500 MB 7505704 5003803
------------------------------------------------------------------------------------------sh: bun benchmark/stream.js -file AS_HOUSES_PARAMS.XML
file: ./AS_HOUSES_PARAMS.XML
------------------------------------------------------------------------------------------
only load - total: 29979.80 time: 29.69 4.74 GB
easysax ns=on uq=on attr=on - total: 53994.98 time: 21257.70 4.74 GB 27997407 1
easysax ns=off uq=on attr=on - total: 50518.53 time: 17841.35 4.74 GB 27997407 1
easysax ns=off uq=off attr=on - total: 47360.99 time: 14886.36 4.74 GB 27997407 1
easysax ns=off uq=off attr=off - total: 42390.00 time: 10174.52 4.74 GB 27997407 1
eksml uq=off attr=on - total: 58463.19 time: 25675.42 4.74 GB 27997407 1
ltx uq=on attr=on - total: 89953.37 time: 56807.52 4.74 GB 27997407 1
saxes uq=on attr=on - total: 123178.7 time: 89020.67 4.74 GB 27997407 0
------------------------------------------------------------------------------------------sh: node benchmark/bench-01.js
count - 100000
size - 34
----------------------------------------------
easysax ns=on uq=on attr=on : 124.97 ms
easysax ns=off uq=on attr=on : 71.09 ms
easysax ns=off uq=off attr=on : 67.30 ms
easysax ns=off uq=off attr=off : 52.92 ms
eksml uq=off attr=on : 111.99 ms
saxen ns=off uq=on attr=on : 94.97 ms
saxophone uq=off attr=on : 69.96 ms
ltx uq=on attr=on : 88.91 ms
saxes uq=on attr=on : 174.89 ms
saxjs uq=on attr=on : 245.46 ms
libxml : 1184.2 ms
expat : 1102.1 ms
saxwasm~481 : 513.93 ms
tuananh uq=off attr=on : 2778.8 ms
----------------------------------------------sh: node bench-02.js
count - 1000
size - 22736
----------------------------------------------
easysax ns=on uq=on attr=on : 104.48 ms
easysax ns=off uq=on attr=on : 75.82 ms
easysax ns=off uq=off attr=on : 54.09 ms
easysax ns=off uq=off attr=off : 45.54 ms
eksml uq=off attr=on : 68.54 ms
saxen ns=off uq=on attr=on : 67.67 ms
saxophone uq=off attr=on : 83.87 ms
ltx uq=on attr=on : 130.20 ms
saxes uq=on attr=on : 157.29 ms
saxjs uq=on attr=on : 576.21 ms
libxml : 1362.6 ms
expat : 1174.6 ms
saxwasm~481 : 436.54 ms
tuananh uq=off attr=on : 451.34 ms
----------------------------------------------sh: node bench-03.js
count - 1000
size - 121786
----------------------------------------------
easysax ns=on uq=on attr=on : 691.52 ms
easysax ns=off uq=on attr=on : 489.07 ms
easysax ns=off uq=off attr=on : 389.16 ms
easysax ns=off uq=off attr=off : 319.11 ms
eksml uq=off attr=on : 420.79 ms
saxen ns=off uq=on attr=on : 837.77 ms
saxophone uq=off attr=on : 681.66 ms
ltx uq=on attr=on : 920.86 ms
saxes uq=on attr=on : 1155.2 ms
saxjs uq=on attr=on : 4305.0 ms
libxml : 7069.5 ms
expat : 7421.8 ms
saxwasm~481 : 3548.3 ms
tuananh uq=off attr=on : 1993.5 ms
----------------------------------------------Example of use
var parser = new EasySax();
// if namespace is required
parser.ns('rss', {
'http://www.w3.org/2005/Atom': 'atom',
'http://www.w3.org/1999/xhtml': 'xhtml',
'http://search.yahoo.com/mrss/': 'media',
'http://purl.org/rss/1.0/': 'rss',
'http://purl.org/dc/elements/1.1/': 'dc',
'http://www.w3.org/1999/02/22-rdf-syntax-ns#' : 'rdf',
'http://purl.org/rss/1.0/modules/content/': 'content',
'http://www.yandex.ru': 'yandex',
'http://news.yandex.ru': 'yandex',
'http://backend.userland.com/rss2': 'rss'
});
parser.on('error', function(msg) {
// console.log('error - ' + msg);
});
parser.on('opentag', function(elementName, attrs, isTagEnd) {
// elementName -- (string) element name. If namespaces are enabled, it automatically sets the prefix
// attrs -- (object) object with attributes
// isTagEnd -- (boolean) flag that the element is empty "<elem/>"
});
parser.on('closetag', function(elementName, isTagStart) {
// isTagStart -- (boolean) flag that the element is empty "<elem/>"
});
parser.on('text', function(text) {
// text -- (String) line of text
});
parser.on('cdata', function(text) {
// text -- (String) CDATA element text string
});
parser.on('comment', function(text) {
// text - (String) comment text
});
//parser.on('question', function() {}); // <? ... ?>
//parser.on('attention', function() {}); // <!XXXXX zzzz="eeee">
parser.write(stringChunk);
parser.write(stringChunk);
...
parser.end(stringChunk);
API Reference
Constructor Options
You can pass a configuration object when creating a new instance: new EasySax(config)
| Parameter | Description | Default |
| :--- | :--- | :--- |
| autoEntity (boolean) | Automatically decode HTML entities (&, <, ", etc.) in text nodes. | true |
| lazy (boolean) | If true, passes a getAttr() function to opentag for lazy attribute evaluation (saves memory/CPU). If false, attributes are evaluated immediately as an object. | false |
| strict (boolean) | Enables strict parsing mode with rigorous XML syntax validation. Recommended if you are unsure about the quality of the input XML | false |
| defaultNS (string) | Root element name for namespace rules. If empty, namespace processing is disabled. | '' |
| ns (object) | Namespace mapping object { 'http://uri': 'prefix' }. Works only if defaultNS is set. | null |
| on (object) | Object for bulk event subscription on initialization. Format: { opentag: fn, text: fn, ... }. | undefined |
| intern (boolean) | Enables string interning. Repeated strings (tag names, attributes) are deduplicated via Map, saving memory on large files. | true |
| map (Map) | Custom Map object for storing interned strings. Allows sharing a single string pool across multiple parser instances. | new Map() |
| salt (number) | Salt for the string hashing algorithm. Useful for isolating pools of different parsers when sharing a map. | null |
| entityDecode (function) | Custom function for entity decoding. Overrides the built-in decoder. | Built-in function |
Methods
| Method | Description |
| :--- | :--- |
| setup(config) | Applies or updates parser settings after creation. Accepts the same config object as the constructor. |
| on(event, cb) | Subscribes a callback to a parsing event. Events: opentag, closetag, text, cdata, comment, error, question, attention, unknownNS. Passing null unsubscribes. |
| ns(root, nsMap) | Sets namespace rules. root is the root element name, nsMap is { 'URI': 'prefix' }. Calling ns(null) disables NS. Returns the parser instance (chainable). |
| write(chunk) | Feeds a chunk of XML data to the parser. Can be called multiple times for streaming. Ignored if parsing was stopped via stop(). |
| end([chunk]) | Finalizes the parsing process. Optionally accepts a final data chunk. Resets internal state, freeing memory. |
| parse(xml) | Convenience method to parse a small XML string entirely. Automatically calls write(xml) then end(). |
| stop() | Forcefully stops parsing. Sets an internal flag, after which write() calls are ignored. Useful for early exit when target data is found. |
| getNodeString() | Returns the raw XML string of the current node being parsed. |