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sax js

A sax-style parser for XML and HTML.

Designed with node 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 <tt><!DOCTYPE</tt>s and <tt><!ENTITY</tt>s

The parser will handle the basic XML entities in text nodes and attribute values: `& < > ' "`. 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.createWriteStream("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.
- `lowercase` - Boolean. If true, then lowercase tag names and attribute names in loose mode, rather than uppercasing them.
- `xmlns` - Boolean. If true, then namespaces are supported.
- `position` - Boolean. If false, then don't track line/col/position.
- `strictEntities` - Boolean. If true, only parse predefined XML entities (`&`, `'`, `>`, `<`, and `"`)

# 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.

`opentagstart` - Emitted immediately when the tag name is available, but before any attributes are encountered. Argument: object with a `name` field and an empty `attributes` set. Note that this is the same object that will later be emitted in the `opentag` event.

`opentag` - An opening tag. Argument: object with `name` and `attributes`. In non-strict mode, tag names are uppercased, unless the `lowercase` 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`. In non-strict mode, attribute names are uppercased, unless the `lowercase` option is set. If the `xmlns` option is set, it will also contains namespace information.

`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.