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JSONStream

streaming JSON.parse and stringify

# install

## example
``` js
var request = require('request')
, JSONStream = require('JSONStream')
, es = require('event-stream')
request({url: 'http://isaacs.couchone.com/registry/_all_docs'})
.pipe(JSONStream.parse('rows.*'))
.pipe(es.mapSync(function (data) {
console.error(data)
return data
}))

# JSONStream.parse(path)

parse stream of values that match a path

JSONStream.parse('rows.*.doc')

The `..` operator is the recursive descent operator from JSONPath, which will match a child at any depth (see examples below).

If your keys have keys that include `.` or `*` etc, use an array instead. ‘['row’, true, /^doc/]`.

If you use an array, `RegExp`s, booleans, and/or functions. The `..` operator is also available in array representation, using `{recurse: true}`. any object that matches the path will be emitted as 'data' (and `pipe`d down stream)

If `path` is empty or null, no 'data' events are emitted.

If you want to have keys emitted, you can prefix your `*` operator with `$`: `obj.$*` - in this case the data passed to the stream is an object with a `key` holding the key and a `value` property holding the data.

## Examples

query a couchdb view:

curl -sS localhost:5984/tests/_all_docs&include_docs=true

you will get something like this:

{"total_rows":129,"offset":0,"rows":[
{ "id":"change1_0.6995461115147918"
, "key":"change1_0.6995461115147918"
, "value":{"rev":"1-e240bae28c7bb3667f02760f6398d508"}
, "doc":{
"_id": "change1_0.6995461115147918"
, "_rev": "1-e240bae28c7bb3667f02760f6398d508","hello":1}
},
{ "id":"change2_0.6995461115147918"
, "key":"change2_0.6995461115147918"
, "value":{"rev":"1-13677d36b98c0c075145bb8975105153"}
, "doc":{
"_id":"change2_0.6995461115147918"
, "_rev":"1-13677d36b98c0c075145bb8975105153"
, "hello":2
}
},
]}

we are probably most interested in the `rows.*.doc`

create a `Stream` that parses the documents from the feed like this:

var stream = JSONStream.parse(['rows', true, 'doc']) //rows, ANYTHING, doc
stream.on('data', function(data) {
console.log('received:', data);
});
//emits anything from _before_ the first match
stream.on('header', function (data) {
console.log('header:', data) // => {"total_rows":129,"offset":0}
})

awesome!

In case you wanted the contents the doc emitted:

var stream = JSONStream.parse(['rows', true, 'doc', {emitKey: true}]) //rows, ANYTHING, doc, items in docs with keys
stream.on('data', function(data) {
console.log('key:', data.key);
console.log('value:', data.value);
});

You can also emit the path:

var stream = JSONStream.parse(['rows', true, 'doc', {emitPath: true}]) //rows, ANYTHING, doc, items in docs with keys
stream.on('data', function(data) {
console.log('path:', data.path);
console.log('value:', data.value);
});

## recursive patterns (..)

‘JSONStream.parse('docs..value’)`(or`JSONStream.parse(['docs', {recurse: true}, 'value'])`using an array) will emit every`value`object that is a child, grand-child, etc. of the` docs` object. In this example, it will match exactly 5 times at various depth levels, emitting 0, 1, 2, 3 and 4 as results.

{
"total": 5,
"docs": [
{
"key": {
"value": 0,
"some": "property"
}
},
{"value": 1},
{"value": 2},
{"blbl": [{}, {"a":0, "b":1, "value":3}, 10]},
{"value": 4}
]
}

# JSONStream.parse(pattern, map)

provide a function that can be used to map or filter the json output. `map` is passed the value at that node of the pattern, if `map` return non-nullish (anything but `null` or `undefined`) that value will be emitted in the stream. If it returns a nullish value, nothing will be emitted.

`JSONStream` also emits ‘'header’`and`'footer'`events, the`'header'`event contains anything in the output that was before the first match, and the`'footer'`, is anything after the last match.

# JSONStream.stringify(open, sep, close)

Create a writable stream.

you may pass in custom `open`, `close`, and `seperator` strings. But, by default, `JSONStream.stringify()` will create an array, (with default options ‘open=’[
', sep='
,
', close='
]
'`)

If you call `JSONStream.stringify(false)` the elements will only be seperated by a newline.

If you only write one item this will be valid JSON.

If you write many items, you can use a `RegExp` to split it into valid chunks.

# JSONStream.stringifyObject(open, sep, close)

Very much like `JSONStream.stringify`, but creates a writable stream for objects instead of arrays.

Accordingly, ‘open=’{
', sep='
,
', close='
}
'`.

When you `.write()` to the stream you must supply an array with `[ key, data ]` as the first argument.

# unix tool

query npm to see all the modules that browserify has ever depended on.

curl https://registry.npmjs.org/browserify | JSONStream 'versions.*.dependencies'

# numbers

numbers will be emitted as numbers. huge numbers that cannot be represented in memory as javascript numbers will be emitted as strings. cf https://github.com/creationix/jsonparse/commit/044b268f01c4b8f97fb936fc85d3bcfba179e5bb for details.

# Acknowlegements

this module depends on https://github.com/creationix/jsonparse by Tim Caswell and also thanks to Florent Jaby for teaching me about parsing with: https://github.com/Floby/node-json-streams

# license

Dual-licensed under the MIT License or the Apache License, version 2.0