JSONWriter

Streaming writer for GeoJSON encoded files.

Loader	Characteristic
File Extension	.geojson
Media Type	application/geo+json
File Type	Text
File Format	JSON
Data Format	Classic Table
Supported APIs	encode, encodeSync, encodeÓInBatches

Usage

For simple usage, you can encode a table into a JSON "file" atomically:

import {JSONWriter} from '@loaders.gl/json';
import {encode} from '@loaders.gl/core';

const data = await encode(url, JSONWriter, {json: options});

Streaming and JSON paths

For larger files, JSONWriter supports streaming JSON parsing, in which case it will yield "batches" of rows from one array.

import {JSONWriter} from '@loaders.gl/json';
import {encodeInBatches} from '@loaders.gl/core';

const batches = await encodeInBatches('geojson.json', JSONWriter, {json: {jsonpaths: ['$.features']}});

for await (const batch of batches) {
  // batch.data will contain a number of rows
  for (const feature of batch.data) {
    switch (feature.geometry.type) {
      case 'Polygon':
      ...
    }
  }
}

To parse a stream of GeoJSON, the user can specify the options.json.jsonpaths to stream the features array.

If no JSONPath is specified the loader will stream the first array it encounters in the JSON payload.

Data Format

Encoded batches are array buffers or strings

Options

Supports table category options such as batchType and batchSize.

Option	From	Type	Default	Description
json.table	[]	boolean	false	Parses non-streaming JSON as table, i.e. return the first embedded array in the JSON. Always true during batched/streaming parsing.
json.jsonpaths	[]	string[]	[]	A list of JSON paths (see below) indicating the array that can be streamed.

JSONPaths

A minimal subset of the JSONPath syntax is supported, to specify which array in a JSON object should be streamed as batchs.

$.component1.component2.component3

• No support for wildcards, brackets etc. Only paths starting with $ (JSON root) are supported.
• Regardless of the paths provided, only arrays will be streamed.

Attribution

This loader is based on a fork of dscape's clarinet under BSD 2-clause license.