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1# sax js
2
3A sax-style parser for XML and HTML.
4
5Designed with [node](http://nodejs.org/) in mind, but should work fine in
6the browser or other CommonJS implementations.
7
8## What This Is
9
10* A very simple tool to parse through an XML string.
11* A stepping stone to a streaming HTML parser.
12* A handy way to deal with RSS and other mostly-ok-but-kinda-broken XML
13 docs.
14
15## What This Is (probably) Not
16
17* An HTML Parser - That's a fine goal, but this isn't it. It's just
18 XML.
19* A DOM Builder - You can use it to build an object model out of XML,
20 but it doesn't do that out of the box.
21* XSLT - No DOM = no querying.
22* 100% Compliant with (some other SAX implementation) - Most SAX
23 implementations are in Java and do a lot more than this does.
24* An XML Validator - It does a little validation when in strict mode, but
25 not much.
26* A Schema-Aware XSD Thing - Schemas are an exercise in fetishistic
27 masochism.
28* A DTD-aware Thing - Fetching DTDs is a much bigger job.
29
30## Regarding `<!DOCTYPE`s and `<!ENTITY`s
31
32The parser will handle the basic XML entities in text nodes and attribute
33values: `&amp; &lt; &gt; &apos; &quot;`. It's possible to define additional
34entities in XML by putting them in the DTD. This parser doesn't do anything
35with that. If you want to listen to the `ondoctype` event, and then fetch
36the doctypes, and read the entities and add them to `parser.ENTITIES`, then
37be my guest.
38
39Unknown entities will fail in strict mode, and in loose mode, will pass
40through unmolested.
41
42## Usage
43
44```javascript
45var sax = require("./lib/sax"),
46 strict = true, // set to false for html-mode
47 parser = sax.parser(strict);
48
49parser.onerror = function (e) {
50 // an error happened.
51};
52parser.ontext = function (t) {
53 // got some text. t is the string of text.
54};
55parser.onopentag = function (node) {
56 // opened a tag. node has "name" and "attributes"
57};
58parser.onattribute = function (attr) {
59 // an attribute. attr has "name" and "value"
60};
61parser.onend = function () {
62 // parser stream is done, and ready to have more stuff written to it.
63};
64
65parser.write('<xml>Hello, <who name="world">world</who>!</xml>').close();
66
67// stream usage
68// takes the same options as the parser
69var saxStream = require("sax").createStream(strict, options)
70saxStream.on("error", function (e) {
71 // unhandled errors will throw, since this is a proper node
72 // event emitter.
73 console.error("error!", e)
74 // clear the error
75 this._parser.error = null
76 this._parser.resume()
77})
78saxStream.on("opentag", function (node) {
79 // same object as above
80})
81// pipe is supported, and it's readable/writable
82// same chunks coming in also go out.
83fs.createReadStream("file.xml")
84 .pipe(saxStream)
85 .pipe(fs.createWriteStream("file-copy.xml"))
86```
87
88
89## Arguments
90
91Pass the following arguments to the parser function. All are optional.
92
93`strict` - Boolean. Whether or not to be a jerk. Default: `false`.
94
95`opt` - Object bag of settings regarding string formatting. All default to `false`.
96
97Settings supported:
98
99* `trim` - Boolean. Whether or not to trim text and comment nodes.
100* `normalize` - Boolean. If true, then turn any whitespace into a single
101 space.
102* `lowercase` - Boolean. If true, then lowercase tag names and attribute names
103 in loose mode, rather than uppercasing them.
104* `xmlns` - Boolean. If true, then namespaces are supported.
105* `position` - Boolean. If false, then don't track line/col/position.
106* `strictEntities` - Boolean. If true, only parse [predefined XML
107 entities](http://www.w3.org/TR/REC-xml/#sec-predefined-ent)
108 (`&amp;`, `&apos;`, `&gt;`, `&lt;`, and `&quot;`)
109
110## Methods
111
112`write` - Write bytes onto the stream. You don't have to do this all at
113once. You can keep writing as much as you want.
114
115`close` - Close the stream. Once closed, no more data may be written until
116it is done processing the buffer, which is signaled by the `end` event.
117
118`resume` - To gracefully handle errors, assign a listener to the `error`
119event. Then, when the error is taken care of, you can call `resume` to
120continue parsing. Otherwise, the parser will not continue while in an error
121state.
122
123## Members
124
125At all times, the parser object will have the following members:
126
127`line`, `column`, `position` - Indications of the position in the XML
128document where the parser currently is looking.
129
130`startTagPosition` - Indicates the position where the current tag starts.
131
132`closed` - Boolean indicating whether or not the parser can be written to.
133If it's `true`, then wait for the `ready` event to write again.
134
135`strict` - Boolean indicating whether or not the parser is a jerk.
136
137`opt` - Any options passed into the constructor.
138
139`tag` - The current tag being dealt with.
140
141And a bunch of other stuff that you probably shouldn't touch.
142
143## Events
144
145All events emit with a single argument. To listen to an event, assign a
146function to `on<eventname>`. Functions get executed in the this-context of
147the parser object. The list of supported events are also in the exported
148`EVENTS` array.
149
150When using the stream interface, assign handlers using the EventEmitter
151`on` function in the normal fashion.
152
153`error` - Indication that something bad happened. The error will be hanging
154out on `parser.error`, and must be deleted before parsing can continue. By
155listening to this event, you can keep an eye on that kind of stuff. Note:
156this happens *much* more in strict mode. Argument: instance of `Error`.
157
158`text` - Text node. Argument: string of text.
159
160`doctype` - The `<!DOCTYPE` declaration. Argument: doctype string.
161
162`processinginstruction` - Stuff like `<?xml foo="blerg" ?>`. Argument:
163object with `name` and `body` members. Attributes are not parsed, as
164processing instructions have implementation dependent semantics.
165
166`sgmldeclaration` - Random SGML declarations. Stuff like `<!ENTITY p>`
167would trigger this kind of event. This is a weird thing to support, so it
168might go away at some point. SAX isn't intended to be used to parse SGML,
169after all.
170
171`opentagstart` - Emitted immediately when the tag name is available,
172but before any attributes are encountered. Argument: object with a
173`name` field and an empty `attributes` set. Note that this is the
174same object that will later be emitted in the `opentag` event.
175
176`opentag` - An opening tag. Argument: object with `name` and `attributes`.
177In non-strict mode, tag names are uppercased, unless the `lowercase`
178option is set. If the `xmlns` option is set, then it will contain
179namespace binding information on the `ns` member, and will have a
180`local`, `prefix`, and `uri` member.
181
182`closetag` - A closing tag. In loose mode, tags are auto-closed if their
183parent closes. In strict mode, well-formedness is enforced. Note that
184self-closing tags will have `closeTag` emitted immediately after `openTag`.
185Argument: tag name.
186
187`attribute` - An attribute node. Argument: object with `name` and `value`.
188In non-strict mode, attribute names are uppercased, unless the `lowercase`
189option is set. If the `xmlns` option is set, it will also contains namespace
190information.
191
192`comment` - A comment node. Argument: the string of the comment.
193
194`opencdata` - The opening tag of a `<![CDATA[` block.
195
196`cdata` - The text of a `<![CDATA[` block. Since `<![CDATA[` blocks can get
197quite large, this event may fire multiple times for a single block, if it
198is broken up into multiple `write()`s. Argument: the string of random
199character data.
200
201`closecdata` - The closing tag (`]]>`) of a `<![CDATA[` block.
202
203`opennamespace` - If the `xmlns` option is set, then this event will
204signal the start of a new namespace binding.
205
206`closenamespace` - If the `xmlns` option is set, then this event will
207signal the end of a namespace binding.
208
209`end` - Indication that the closed stream has ended.
210
211`ready` - Indication that the stream has reset, and is ready to be written
212to.
213
214`noscript` - In non-strict mode, `<script>` tags trigger a `"script"`
215event, and their contents are not checked for special xml characters.
216If you pass `noscript: true`, then this behavior is suppressed.
217
218## Reporting Problems
219
220It's best to write a failing test if you find an issue. I will always
221accept pull requests with failing tests if they demonstrate intended
222behavior, but it is very hard to figure out what issue you're describing
223without a test. Writing a test is also the best way for you yourself
224to figure out if you really understand the issue you think you have with
225sax-js.
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