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226 lines
8.2 KiB
Markdown
226 lines
8.2 KiB
Markdown
# sax js
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A sax-style parser for XML and HTML.
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Designed with [node](http://nodejs.org/) in mind, but should work fine in
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the browser or other CommonJS implementations.
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## What This Is
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* A very simple tool to parse through an XML string.
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* A stepping stone to a streaming HTML parser.
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* A handy way to deal with RSS and other mostly-ok-but-kinda-broken XML
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docs.
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## What This Is (probably) Not
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* An HTML Parser - That's a fine goal, but this isn't it. It's just
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XML.
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* A DOM Builder - You can use it to build an object model out of XML,
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but it doesn't do that out of the box.
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* XSLT - No DOM = no querying.
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* 100% Compliant with (some other SAX implementation) - Most SAX
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implementations are in Java and do a lot more than this does.
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* An XML Validator - It does a little validation when in strict mode, but
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not much.
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* A Schema-Aware XSD Thing - Schemas are an exercise in fetishistic
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masochism.
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* A DTD-aware Thing - Fetching DTDs is a much bigger job.
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## Regarding `<!DOCTYPE`s and `<!ENTITY`s
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The parser will handle the basic XML entities in text nodes and attribute
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values: `& < > ' "`. It's possible to define additional
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entities in XML by putting them in the DTD. This parser doesn't do anything
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with that. If you want to listen to the `ondoctype` event, and then fetch
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the doctypes, and read the entities and add them to `parser.ENTITIES`, then
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be my guest.
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Unknown entities will fail in strict mode, and in loose mode, will pass
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through unmolested.
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## Usage
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```javascript
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var sax = require("./lib/sax"),
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strict = true, // set to false for html-mode
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parser = sax.parser(strict);
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parser.onerror = function (e) {
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// an error happened.
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};
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parser.ontext = function (t) {
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// got some text. t is the string of text.
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};
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parser.onopentag = function (node) {
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// opened a tag. node has "name" and "attributes"
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};
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parser.onattribute = function (attr) {
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// an attribute. attr has "name" and "value"
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};
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parser.onend = function () {
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// parser stream is done, and ready to have more stuff written to it.
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};
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parser.write('<xml>Hello, <who name="world">world</who>!</xml>').close();
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// stream usage
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// takes the same options as the parser
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var saxStream = require("sax").createStream(strict, options)
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saxStream.on("error", function (e) {
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// unhandled errors will throw, since this is a proper node
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// event emitter.
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console.error("error!", e)
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// clear the error
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this._parser.error = null
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this._parser.resume()
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})
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saxStream.on("opentag", function (node) {
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// same object as above
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})
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// pipe is supported, and it's readable/writable
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// same chunks coming in also go out.
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fs.createReadStream("file.xml")
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.pipe(saxStream)
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.pipe(fs.createWriteStream("file-copy.xml"))
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```
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## Arguments
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Pass the following arguments to the parser function. All are optional.
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`strict` - Boolean. Whether or not to be a jerk. Default: `false`.
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`opt` - Object bag of settings regarding string formatting. All default to `false`.
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Settings supported:
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* `trim` - Boolean. Whether or not to trim text and comment nodes.
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* `normalize` - Boolean. If true, then turn any whitespace into a single
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space.
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* `lowercase` - Boolean. If true, then lowercase tag names and attribute names
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in loose mode, rather than uppercasing them.
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* `xmlns` - Boolean. If true, then namespaces are supported.
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* `position` - Boolean. If false, then don't track line/col/position.
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* `strictEntities` - Boolean. If true, only parse [predefined XML
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entities](http://www.w3.org/TR/REC-xml/#sec-predefined-ent)
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(`&`, `'`, `>`, `<`, and `"`)
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## Methods
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`write` - Write bytes onto the stream. You don't have to do this all at
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once. You can keep writing as much as you want.
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`close` - Close the stream. Once closed, no more data may be written until
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it is done processing the buffer, which is signaled by the `end` event.
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`resume` - To gracefully handle errors, assign a listener to the `error`
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event. Then, when the error is taken care of, you can call `resume` to
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continue parsing. Otherwise, the parser will not continue while in an error
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state.
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## Members
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At all times, the parser object will have the following members:
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`line`, `column`, `position` - Indications of the position in the XML
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document where the parser currently is looking.
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`startTagPosition` - Indicates the position where the current tag starts.
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`closed` - Boolean indicating whether or not the parser can be written to.
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If it's `true`, then wait for the `ready` event to write again.
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`strict` - Boolean indicating whether or not the parser is a jerk.
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`opt` - Any options passed into the constructor.
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`tag` - The current tag being dealt with.
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And a bunch of other stuff that you probably shouldn't touch.
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## Events
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All events emit with a single argument. To listen to an event, assign a
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function to `on<eventname>`. Functions get executed in the this-context of
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the parser object. The list of supported events are also in the exported
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`EVENTS` array.
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When using the stream interface, assign handlers using the EventEmitter
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`on` function in the normal fashion.
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`error` - Indication that something bad happened. The error will be hanging
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out on `parser.error`, and must be deleted before parsing can continue. By
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listening to this event, you can keep an eye on that kind of stuff. Note:
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this happens *much* more in strict mode. Argument: instance of `Error`.
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`text` - Text node. Argument: string of text.
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`doctype` - The `<!DOCTYPE` declaration. Argument: doctype string.
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`processinginstruction` - Stuff like `<?xml foo="blerg" ?>`. Argument:
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object with `name` and `body` members. Attributes are not parsed, as
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processing instructions have implementation dependent semantics.
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`sgmldeclaration` - Random SGML declarations. Stuff like `<!ENTITY p>`
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would trigger this kind of event. This is a weird thing to support, so it
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might go away at some point. SAX isn't intended to be used to parse SGML,
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after all.
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`opentagstart` - Emitted immediately when the tag name is available,
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but before any attributes are encountered. Argument: object with a
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`name` field and an empty `attributes` set. Note that this is the
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same object that will later be emitted in the `opentag` event.
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`opentag` - An opening tag. Argument: object with `name` and `attributes`.
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In non-strict mode, tag names are uppercased, unless the `lowercase`
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option is set. If the `xmlns` option is set, then it will contain
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namespace binding information on the `ns` member, and will have a
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`local`, `prefix`, and `uri` member.
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`closetag` - A closing tag. In loose mode, tags are auto-closed if their
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parent closes. In strict mode, well-formedness is enforced. Note that
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self-closing tags will have `closeTag` emitted immediately after `openTag`.
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Argument: tag name.
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`attribute` - An attribute node. Argument: object with `name` and `value`.
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In non-strict mode, attribute names are uppercased, unless the `lowercase`
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option is set. If the `xmlns` option is set, it will also contains namespace
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information.
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`comment` - A comment node. Argument: the string of the comment.
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`opencdata` - The opening tag of a `<![CDATA[` block.
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`cdata` - The text of a `<![CDATA[` block. Since `<![CDATA[` blocks can get
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quite large, this event may fire multiple times for a single block, if it
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is broken up into multiple `write()`s. Argument: the string of random
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character data.
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`closecdata` - The closing tag (`]]>`) of a `<![CDATA[` block.
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`opennamespace` - If the `xmlns` option is set, then this event will
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signal the start of a new namespace binding.
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`closenamespace` - If the `xmlns` option is set, then this event will
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signal the end of a namespace binding.
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`end` - Indication that the closed stream has ended.
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`ready` - Indication that the stream has reset, and is ready to be written
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to.
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`noscript` - In non-strict mode, `<script>` tags trigger a `"script"`
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event, and their contents are not checked for special xml characters.
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If you pass `noscript: true`, then this behavior is suppressed.
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## Reporting Problems
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It's best to write a failing test if you find an issue. I will always
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accept pull requests with failing tests if they demonstrate intended
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behavior, but it is very hard to figure out what issue you're describing
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without a test. Writing a test is also the best way for you yourself
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to figure out if you really understand the issue you think you have with
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sax-js.
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