Dominic Tarr's JSONStream using Rodd Vaggs' through2
npm install jsonstream2Dominic Tarr's JSONStream using Rodd Vagg's through2.
``sh`
npm install jsonstream2
`js
var request = require('request')
, JSONStream = require('jsonstream2')
, 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
}))
`
parse stream of values that match a path
`js`
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, RegExps, booleans, and/or functions. The .. operator is also available in array representation, using {recurse: true}.pipe
any object that matches the path will be emitted as 'data' (and 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.
query a couchdb view:
`sh`
curl -sS localhost:5984/tests/_all_docs&include_docs=true
you will get something like this:
`js
{"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:
`js
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:
`js
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:
`js
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);
});
`
JSONStream.parse('docs..value') JSONStream.parse(['docs', {recurse: true}, 'value'])
(or using an array)value
will emit every 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.
`js`
{
"total": 5,
"docs": [
{
"key": {
"value": 0,
"some": "property"
}
},
{"value": 1},
{"value": 2},
{"blbl": [{}, {"a":0, "b":1, "value":3}, 10]},
{"value": 4}
]
}
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,map
if 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,'header'
the event contains anything in the output that was before'footer'
the first match, and the , is anything after the last match.
Create a writable stream.
you may pass in custom open, close, and seperator strings.JSONStream.stringify()
But, by default, will create an array,open='[\n', sep='\n,\n', close='\n]\n'
(with default options )
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.
Very much like JSONStream.stringify,
but creates a writable stream for objects instead of arrays.
Accordingly, open='{\n', sep='\n,\n', close='\n}\n'.
When you .write() to the stream you must supply an array with [ key, data ]
as the first argument.
query npm to see all the modules that browserify has ever depended on.
`sh``
curl https://registry.npmjs.org/browserify | JSONStream 'versions.*.dependencies'
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.
this module depends on https://github.com/creationix/jsonparse
by Tim Caswell. Thanks also to Florent Jaby for https://github.com/Floby/node-json-streams
MIT