Main module

The main module's default export is parserStream — a shortcut for parser.asStream(options) that returns the parser as a Duplex stream. The named export parser exposes the underlying parser factory.

Introduction

import parserStream from 'stream-json';
import fs from 'node:fs';

const pipeline = fs.createReadStream('sample.json').pipe(parserStream());

let objectCounter = 0;
pipeline.on('data', data => data.name === 'startObject' && ++objectCounter);
pipeline.on('end', () => console.log(`Found ${objectCounter} objects.`));

API

parserStream(options?) takes one optional argument: Parser options, and returns a Duplex stream. The writable side accepts text (Buffer/string), the readable side emits {name, value} token objects.

// parserStream is literally parser.asStream:
const parserStream = parser.asStream;

In 2.x this entry was called make() and bundled an emit() decoration so consumers could subscribe to token-name events (startObject, keyValue, …) directly on the returned stream. In 3.x the bundled emit() is gone — compose it explicitly when you want the event API. See Migrating from 2.x to 3.x.

SAX-style events with emit()

If you want token-name events on the stream, wrap with emit() from utils:

import parserStream from 'stream-json';
import emit from 'stream-json/utils/emit.js';
import fs from 'node:fs';

const pipeline = emit(fs.createReadStream('sample.json').pipe(parserStream()));

let objectCounter = 0;
pipeline.on('startObject', () => ++objectCounter);
pipeline.on('end', () => console.log(`Found ${objectCounter} objects.`));

Named exports

parser

Re-exports the parser factory.

import {parser} from 'stream-json';
import fs from 'node:fs';

const pipeline = fs.createReadStream('sample.json').pipe(parser.asStream());

let objectCounter = 0;
pipeline.on('data', data => data.name === 'startObject' && ++objectCounter);
pipeline.on('end', () => console.log(`Found ${objectCounter} objects.`));

parserStream

The same value as the default export — provided as a named mirror so it composes with other named imports:

import {parserStream, parser} from 'stream-json';

Web entry

For Web Streams substrate, stream-json/web mirrors the main entry. The default export is parserWebStream, a shortcut for parser.asWebStream(options) that returns a {readable, writable} pair. The named export parser is the underlying parser factory from stream-json/web/parser.js.

import parserWebStream from 'stream-json/web';
import {parser} from 'stream-json/web';

const {readable, writable} = parserWebStream();
sourceReadable.pipeTo(writable);
for await (const tok of readable) console.log(tok);

The Web entry pulls in no Node-stream imports — safe for browser bundles.