jso\nl

Transform a stream of JSON into a stream of Line Delimited JSON

Install

$ npm install --save jsonl

Use

From Buffers

var fs = require("fs")
var jsonl = require("jsonl")

fs.createReadStream("./in.json")
  .pipe(jsonl())
  .pipe(fs.createWriteStream("./out.json"))

in.json

[{"test":"value"},{"test":"value"},{"test":"value"},{"test":"value"}]

out.json

{"test":"value"}
{"test":"value"}
{"test":"value"}
{"test":"value"}

From Objects

var fs = require("fs")
var jsonl = require("jsonl")
var through = require("through2")
var stream = through.obj()

stream.pipe(jsonl({toBufferStream:true}))
  .pipe(fs.createWriteStream("./out.json"))

stream.push({test:"value"})
stream.push({test:"value"})
stream.push({test:"value"})
stream.push({test:"value"})
stream.end()

out.json

{"test":"value"}
{"test":"value"}
{"test":"value"}
{"test":"value"}

Depth

To get the results you expect, you will likely need to know the structure of your incoming data. You may have to pass a depth property, which corresponds to the layer of the property in a serialized, nested JSON object.

By default, jsonl will use a depth of 1 when reading data from a Buffer stream (expecting objects to be nested in an array), and a depth of 0 from a stream in object mode.

/*0*/[
/*1*/  {
/*2*/    test: "value"
/*1*/  },
/*1*/  {
/*2*/    test: "value"
/*1*/  }
/*0*/]

Plucking

To filter the incoming data based on properties, you can select specific fields to be plucked out of the incoming object.

* You will need to specify a depth property for the nested level of the property.

var fs = require("fs")
var jsonl = require("jsonl")

fs.createReadStream("./in.json")
  .pipe(jsonl({pluck:["category"], depth:2}))
  .pipe(fs.createWriteStream("./out.json"))

in.json

[{"category": "cactus heights", "question":"?", "answer": "!"},{"category": "giraffe shoe sizes", "question":"?", "answer": "!"}]

out.json

{"category":"cactus heights"}
{"category":"giraffe shoe sizes"}

API

var jsonl = require("jsonl")([opts])

opts.depth

• Type: Number (default: 1)

The depth of the objects in the incoming data to pluck out. This is what you want for an array of objects, such as:

[{"this":"that"},{"this":"that"}]

opts.objectMode

• Type: Boolean (default: false)

Convert data into an object stream.

opts.pluck

• Type: Array|String (default: [])

Only return select properties from JSON objects.

opts.separator

• Type: String (default: \n)

String to separate object data with.

opts.toBufferStream

• Type: Boolean (default: false)

Set this to true when you have an object stream that you would like converted to a stream of line delimited JSON buffers.

If set, this defaults opts.depth to 0, but can still be overridden.

License

MIT © Stephen Sawchuk