rawStream.pipe(JSONStream.parse()).pipe(streamOfObjects)
npm install jsonstream-nextThis project is a fork of dominictarr/JSONStream that:
- Pulls in PRs that fix bugs and makes them all work
- Adds support for async flush functions
- Promises to be responsive to future PRs + stay up to date
- Update to use latest node and streaming patterns
All thanks and credit goes to the original maintainers!
streaming JSON.parse and stringify
npm install jsonstream-next`example
js
const request = require('request')
const JSONStream = require('jsonstream-next')
const 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
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}.
any object that matches the path will be emitted as 'data' (and piped 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.$3
query a couchdb view:
` bash
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
create a
that parses the documents from the feed like this:` js
var stream = JSONStream.parse(['rows', true, 'doc']) //rows, ANYTHING, docstream.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 keysstream.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 keysstream.on('data', function(data) {
console.log('path:', data.path);
console.log('value:', data.value);
});
`$3
(or 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.`js
{
"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.
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='[\n', sep='\n,\n', close='\n]\n')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
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='{\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.unix tool
query npm to see all the modules that browserify has ever depended on.
bash
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
and also thanks to Florent Jaby for teaching me about parsing with:
https://github.com/Floby/node-json-streams
Dual-licensed under the MIT License or the Apache License, version 2.0