SAX based evented streaming JSON parser in JavaScript (browser and node)
npm install clarinet!NPM Downloads !NPM Version 
clarinet is a sax-like streaming parser for JSON. works in the browser and node.js. clarinet is inspired (and forked) from [sax-js][saxjs]. just like you shouldn't use sax when you need dom you shouldn't use clarinet when you need JSON.parse. for a more detailed introduction and a performance study please refer to this [article][blog].
clarinet is very much like [yajl] but written in javascript:
* written in javascript
* portable
* robust (~110 tests pass before even announcing the project)
* data representation independent
* fast
* generates verbose, useful error messages including context of where
the error occurs in the input text.
* can parse json data off a stream, incrementally
* simple to use
* tiny
the reason behind this work was to create better full text support in node. creating indexes out of large (or many) json files doesn't require a full understanding of the json file, but it does require something like clarinet.
1. install [npm]
2. npm install clarinet
3. var clarinet = require('clarinet');
1. minimize clarinet.js
2. load it into your webpage
`` js
var clarinet = require("clarinet")
, parser = clarinet.parser()
;
parser.onerror = function (e) {
// an error happened. e is the error.
};
parser.onvalue = function (v) {
// got some value. v is the value. can be string, double, bool, or null.
};
parser.onopenobject = function (key) {
// opened an object. key is the first key.
};
parser.onkey = function (key) {
// got a subsequent key in an object.
};
parser.oncloseobject = function () {
// closed an object.
};
parser.onopenarray = function () {
// opened an array.
};
parser.onclosearray = function () {
// closed an array.
};
parser.onend = function () {
// parser stream is done, and ready to have more stuff written to it.
};
parser.write('{"foo": "bar"}').close();
`
` js`
// stream usage
// takes the same options as the parser
var stream = require("clarinet").createStream(options);
stream.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()
})
stream.on("openobject", function (node) {
// same object as above
})
// pipe is supported, and it's readable/writable
// same chunks coming in also go out.
fs.createReadStream("file.json")
.pipe(stream)
.pipe(fs.createReadStream("file-altered.json"))
pass the following arguments to the parser function. all are optional.
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.
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 untilend
it is done processing the buffer, which is signaled by the event.
resume - to gracefully handle errors, assign a listener to the error
event. then, when the error is taken care of, you can call to
continue parsing. otherwise, the parser will not continue while in an error
state.
at all times, the parser object will have the following members:
line, column, position - indications of the position in the json
document where the parser currently is looking.
closed - boolean indicating whether or not the parser can be written to.true
if it's , then wait for the ready event to write again.
opt - any options passed into the constructor.
and a bunch of other stuff that you probably shouldn't touch.
all events emit with a single argument. to listen to an event, assign a
function to on. functions get executed in the this-context ofEVENTS
the parser object. the list of supported events are also in the exported array.
when using the stream interface, assign handlers using the EventEmitter function in the normal fashion.
error - indication that something bad happened. the error will be hangingparser.error
out on , and must be deleted before parsing can continue. byError
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 .
value - a json value. argument: value, can be a bool, null, string on number
openobject - object was opened. argument: key, a string with the first key of the object (if any)
key - an object key: argument: key, a string with the current key. Not called for first key (use openobject for that).
closeobject - indication that an object was closed
openarray - indication that an array was opened
closearray - indication that an array was closed
end - indication that the closed stream has ended.
ready - indication that the stream has reset, and is ready to be written
to.
some [samples] are available to help you get started. one that creates a list of top npm contributors, and another that gets a bunch of data from twitter and generates valid json.
check [issues]
everyone is welcome to contribute. patches, bug-fixes, new features
1. create an [issue][issues] so the community can comment on your idea
2. fork clarinet
3. create a new branch
4. create tests for the changes you made
5. make sure you pass both existing and newly inserted tests
6. commit your changes
7. push to your branch
8. create an pull request
helpful tips:
check index.html. there's two env vars you can set, CRECORD and CDEBUG.
* CRECORD allows you to record the event sequence from a new json test so you don't have to write everything. CDEBUG
* can be set to info or debug. info will console.log all emits, debug will console.log what happens to each char.
in test/clarinet.js there's two lines you might want to change. #8 where you define seps, if you are isolating a test you probably just want to run one sep, so change this array to [undefined]. #718 which says for (var key in docs) { is where you can change the docs you want to run. e.g. to run foobar i would do something like for (var key in {foobar:''}) {.
* code: git clone git://github.com/dscape/clarinet.git
* home:
* bugs:
* build: 
(oO)--',-` in [caos]
[npm]: http://npmjs.org
[issues]: http://github.com/dscape/clarinet/issues
[caos]: http://caos.di.uminho.pt/
[saxjs]: http://github.com/isaacs/sax-js
[yajl]: https://github.com/lloyd/yajl
[samples]: https://github.com/dscape/clarinet/tree/master/samples
[blog]: http://writings.nunojob.com/2011/12/clarinet-sax-based-evented-streaming-json-parser-in-javascript-for-the-browser-and-nodejs.html