# sax js

A sax-style parser for XML and HTML.

Designed with [node](http://nodejs.org/) in mind, but should work fine in
the browser or other CommonJS implementations.

## What This Is

* A very simple tool to parse through an XML string.
* A stepping stone to a streaming HTML parser.
* A handy way to deal with RSS and other mostly-ok-but-kinda-broken XML 
  docs.

## What This Is (probably) Not

* An HTML Parser - That's a fine goal, but this isn't it.  It's just
  XML.
* A DOM Builder - You can use it to build an object model out of XML,
  but it doesn't do that out of the box.
* XSLT - No DOM = no querying.
* 100% Compliant with (some other SAX implementation) - Most SAX
  implementations are in Java and do a lot more than this does.
* An XML Validator - It does a little validation when in strict mode, but
  not much.
* A Schema-Aware XSD Thing - Schemas are an exercise in fetishistic 
  masochism.
* A DTD-aware Thing - Fetching DTDs is a much bigger job.

## Regarding `<!DOCTYPE`s and `<!ENTITY`s

The parser will handle the basic XML entities in text nodes and attribute
values: `&amp; &lt; &gt; &apos; &quot;`. It's possible to define additional
entities in XML by putting them in the DTD. This parser doesn't do anything
with that. If you want to listen to the `ondoctype` event, and then fetch
the doctypes, and read the entities and add them to `parser.ENTITIES`, then
be my guest.

Unknown entities will fail in strict mode, and in loose mode, will pass
through unmolested.

## Usage

    var sax = require("./lib/sax"),
      strict = true, // set to false for html-mode
      parser = sax.parser(strict);

    parser.onerror = function (e) {
      // an error happened.
    };
    parser.ontext = function (t) {
      // got some text.  t is the string of text.
    };
    parser.onopentag = function (node) {
      // opened a tag.  node has "name" and "attributes"
    };
    parser.onattribute = function (attr) {
      // an attribute.  attr has "name" and "value"
    };
    parser.onend = function () {
      // parser stream is done, and ready to have more stuff written to it.
    };

    parser.write('<xml>Hello, <who name="world">world</who>!</xml>').close();

    // stream usage
    // takes the same options as the parser
    var saxStream = require("sax").createStream(strict, options)
    saxStream.on("error", function (e) {
      // unhandled errors will throw, since this is a proper node
      // event emitter.
      console.error("error!", e)
      // clear the error
      this._parser.error = null
      this._parser.resume()
    })
    saxStream.on("opentag", function (node) {
      // same object as above
    })
    // pipe is supported, and it's readable/writable
    // same chunks coming in also go out.
    fs.createReadStream("file.xml")
      .pipe(saxStream)
      .pipe(fs.createReadStream("file-copy.xml"))



## Arguments

Pass the following arguments to the parser function.  All are optional.

`strict` - Boolean. Whether or not to be a jerk. Default: `false`.

`opt` - Object bag of settings regarding string formatting.  All default to `false`.

Settings supported:

* `trim` - Boolean. Whether or not to trim text and comment nodes.
* `normalize` - Boolean. If true, then turn any whitespace into a single
  space.
* `lowercasetags` - Boolean. If true, then lowercase tags in loose mode, 
  rather than uppercasing them.
* `xmlns` - Boolean. If true, then namespaces are supported.

## Methods

`write` - Write bytes onto the stream. You don't have to do this all at
once. You can keep writing as much as you want.

`close` - Close the stream. Once closed, no more data may be written until
it is done processing the buffer, which is signaled by the `end` event.

`resume` - To gracefully handle errors, assign a listener to the `error`
event. Then, when the error is taken care of, you can call `resume` to
continue parsing. Otherwise, the parser will not continue while in an error
state.

## Members

At all times, the parser object will have the following members:

`line`, `column`, `position` - Indications of the position in the XML
document where the parser currently is looking.

`startTagPosition` - Indicates the position where the current tag starts.

`closed` - Boolean indicating whether or not the parser can be written to.
If it's `true`, then wait for the `ready` event to write again.

`strict` - Boolean indicating whether or not the parser is a jerk.

`opt` - Any options passed into the constructor.

`tag` - The current tag being dealt with.

And a bunch of other stuff that you probably shouldn't touch.

## Events

All events emit with a single argument. To listen to an event, assign a
function to `on<eventname>`. Functions get executed in the this-context of
the parser object. The list of supported events are also in the exported
`EVENTS` array.

When using the stream interface, assign handlers using the EventEmitter
`on` function in the normal fashion.

`error` - Indication that something bad happened. The error will be hanging
out on `parser.error`, and must be deleted before parsing can continue. By
listening to this event, you can keep an eye on that kind of stuff. Note:
this happens *much* more in strict mode. Argument: instance of `Error`.

`text` - Text node. Argument: string of text.

`doctype` - The `<!DOCTYPE` declaration. Argument: doctype string.

`processinginstruction` - Stuff like `<?xml foo="blerg" ?>`. Argument:
object with `name` and `body` members. Attributes are not parsed, as
processing instructions have implementation dependent semantics.

`sgmldeclaration` - Random SGML declarations. Stuff like `<!ENTITY p>`
would trigger this kind of event. This is a weird thing to support, so it
might go away at some point. SAX isn't intended to be used to parse SGML,
after all.

`opentag` - An opening tag. Argument: object with `name` and `attributes`.
In non-strict mode, tag names are uppercased, unless the `lowercasetags`
option is set.  If the `xmlns` option is set, then it will contain
namespace binding information on the `ns` member, and will have a
`local`, `prefix`, and `uri` member.

`closetag` - A closing tag. In loose mode, tags are auto-closed if their
parent closes. In strict mode, well-formedness is enforced. Note that
self-closing tags will have `closeTag` emitted immediately after `openTag`.
Argument: tag name.

`attribute` - An attribute node.  Argument: object with `name` and `value`,
and also namespace information if the `xmlns` option flag is set.

`comment` - A comment node.  Argument: the string of the comment.

`opencdata` - The opening tag of a `<![CDATA[` block.

`cdata` - The text of a `<![CDATA[` block. Since `<![CDATA[` blocks can get
quite large, this event may fire multiple times for a single block, if it
is broken up into multiple `write()`s. Argument: the string of random
character data.

`closecdata` - The closing tag (`]]>`) of a `<![CDATA[` block.

`opennamespace` - If the `xmlns` option is set, then this event will
signal the start of a new namespace binding.

`closenamespace` - If the `xmlns` option is set, then this event will
signal the end of a namespace binding.

`end` - Indication that the closed stream has ended.

`ready` - Indication that the stream has reset, and is ready to be written
to.

`noscript` - In non-strict mode, `<script>` tags trigger a `"script"`
event, and their contents are not checked for special xml characters.
If you pass `noscript: true`, then this behavior is suppressed.

## Reporting Problems

It's best to write a failing test if you find an issue.  I will always
accept pull requests with failing tests if they demonstrate intended
behavior, but it is very hard to figure out what issue you're describing
without a test.  Writing a test is also the best way for you yourself
to figure out if you really understand the issue you think you have with
sax-js.
