readme.hbs
node-libxslt
============
[](https://travis-ci.org/albanm/node-libxslt)
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Node.js bindings for [libxslt](http://xmlsoft.org/libxslt/) compatible with [libxmljs](https://github.com/polotek/libxmljs/issues/226).
Installation
------------
npm install libxslt
Basic usage
-----------
```js
var libxslt = require('libxslt');
libxslt.parse(stylesheetString, function(err, stylesheet){
var params = {
MyParam: 'my value'
};
// 'params' parameter is optional
stylesheet.apply(documentString, params, function(err, result){
// err contains any error from parsing the document or applying the stylesheet
// result is a string containing the result of the transformation
});
});
```
Libxmljs integration
--------------------
Node-libxslt depends on [libxmljs](https://github.com/polotek/libxmljs/issues/226) in the same way that [libxslt](http://xmlsoft.org/libxslt/) depends on [libxml](http://xmlsoft.org/). This dependancy makes possible to bundle and to load in memory libxml only once for users of both libraries.
The libxmljs module required by node-libxslt is exposed as ```require('libxslt').libxmljs```. This prevents depending on libxmljs twice which is not optimal and source of weird bugs.
It is possible to work with libxmljs documents instead of strings:
```js
var libxslt = require('libxslt');
var libxmljs = libxslt.libxmljs;
var stylesheetObj = libxmljs.parseXml(stylesheetString, { nocdata: true });
var stylesheet = libxslt.parse(stylesheetObj);
var document = libxmljs.parseXml(documentString);
stylesheet.apply(document, function(err, result){
// result is now a libxmljs document containing the result of the transformation
});
```
This is only useful if you already needed to parse a document before applying the stylesheet for previous manipulations.
Or if you wish to be returned a document instead of a string for ulterior manipulations.
In these cases you will prevent extraneous parsings and serializations.
Includes
--------
XSL includes are supported but relative paths must be given from the execution directory, usually the root of the project.
Includes are resolved when parsing the stylesheet by libxml. Therefore the parsing task becomes IO bound, which is why you should not use synchronous parsing when you expect some includes.
Sync or async
-------------
The same *parse()* and *apply()* functions can be used in synchronous mode simply by removing the callback parameter.
In this case if a parsing error occurs it will be thrown.
```js
var libxslt = require('libxslt');
var stylesheet = libxslt.parse(stylesheetString);
var result = stylesheet.apply(documentString);
```
The asynchronous functions use the [libuv work queue](http://nikhilm.github.io/uvbook/threads.html#libuv-work-queue)
to provide parallelized computation in node.js worker threads. This makes it non-blocking for the main event loop of node.js.
Note that libxmljs parsing doesn't use the work queue, so only a part of the process is actually parallelized.
A small benchmark is available in the project. It has a very limited scope, it uses always the same small transformation a few thousand times.
To run it use:
node benchmark.js
This is an example of its results with an intel core i5 3.1GHz:
```
10000 synchronous parse from parsed doc in 52ms = 192308/s
10000 asynchronous parse in series from parsed doc in 229ms = 43668/s
10000 asynchronous parse in parallel from parsed doc in 56ms = 178571/s
10000 synchronous apply from parsed doc in 329ms = 30395/s
10000 asynchronous apply in series from parsed doc in 569ms = 17575/s
10000 asynchronous apply in parallel from parsed doc in 288ms = 34722/s
```
Observations:
- it's pretty fast !
- asynchronous is slower when running in series.
- asynchronous can become faster when concurrency is high.
Conclusion:
- use asynchronous by default it will be kinder to your main event loop and is pretty fast anyway.
- use synchronous only if you really want the highest performance and expect low concurrency.
- of course you can also use synchronous simply to reduce code depth. If you don't expect a huge load it will be ok.
- DO NOT USE synchronous parsing if there is some includes in your XSL stylesheets.
Environment compatibility
-------------------------
For now 64bits linux and 32bits windows are confirmed. Other environments are probably ok, but not checked. Please report an issue if you encounter some difficulties.
Node-libxslt depends on [node-gyp](https://github.com/TooTallNate/node-gyp), you will need to meet its requirements. This can be a bit painful mostly for windows users. The node-gyp version bundled in your npm will have to be greater than 0.13.0, so you might have to follow [these instructions to upgrade](https://github.com/TooTallNate/node-gyp/wiki/Updating-npm's-bundled-node-gyp). There is no system dependancy otherwise, libxslt is bundled in the project.
API Reference
=============
{{#module name="libxslt"~}}
{{>body~}}
{{>members~}}
{{/module~}}
*documented by [jsdoc-to-markdown](https://github.com/75lb/jsdoc-to-markdown)*.