JSON Stream Parser

JSON Stream Parser: turns stream fragments into JSON values as NDJSON, concatenated values, or one whole document.

Each parse appends the current chunk to a buffer and extracts whatever is now complete. 'NDJSON' takes one value per line and reports a line that does not parse rather than skipping it silently. 'Stream' accepts any concatenation of complete top-level values — whitespace-separated objects, or a JSON array whose elements are emitted as they close — and is safe at every chunk boundary, including one that falls inside a string. 'Single document' holds everything back until the whole buffer is one complete value, then emits it. Text that is not yet a complete value stays in the buffer and shows on pendingCharacters; maxLength stops a malformed stream from growing without bound by clearing the buffer and reporting it. values carries everything the last parse completed, parsed the last of them.

When to use it

A stream whose payloads are JSON but do not arrive one-per-event: NDJSON logs, a chunked HTTP body, an array streamed element by element. Not needed for Server-Sent Events with one JSON object per event — that node already parses each payload onto its Data output.

At a glance

Category	Data
Type name	net.noodl.JSONStreamParser
Available in	browser, cloud
SSR compatibility	safe
Provided by	noodl-runtime

Inputs

Values

Name	Type	Default	Description
chunk	String	—	The next fragment of the stream; boundaries may fall anywhere, including inside a string
format	Enum (ndjson, stream, single)	ndjson	How values are framed on this stream: one per line, any concatenation of complete values, or one whole document
maxLength	Number	1048576	Cap on unparsed text held while a value completes; exceeding it clears the buffer and reports an error rather than growing forever

Signals

Name	Type	Default	Description
clear	Signal	—	Discards the pending text, the parsed values and the error counter
parse	Signal	—	Appends the current Chunk and emits every value that is now complete; the chunk is retained between pulses

Outputs

Values

Name	Type	Default	Description
isComplete	Boolean	—	True when the last Parse left nothing pending, so every value so far was whole
parsed	*	—	The last complete value the most recent Parse produced
pendingCharacters	Number	—	Text held back because a value is not complete yet; persistently non-zero means Format does not match the stream
valueCount	Number	—	How many values have been parsed since the last Clear, across every Parse
values	Array	—	Every value completed by the most recent Parse, in order

Signals

Name	Type	Default	Description
cleared	Signal	—	Fires once the pending text and the values have been discarded
completed	Signal	—	Fires after every invocation, whatever the outcome — wire this to carry on regardless. Failure still fires and still carries its reason, so this cannot hide an error
done	Signal	—	Fires when a Parse consumed text or a Clear discarded something; Success is narrower and fires only when values came out
success	Signal	—	Fires when a Parse yielded at least one value, so a chunk that merely advanced an incomplete value stays quiet
unchanged	Signal	—	Fires when there was nothing pending to parse, or nothing to clear — a valid action with nothing to do

Failure outputs

Name	Type	Default	Description
error	String	—	Why the last value or line would not parse; kept until the next failure or a Clear
errorCount	Number	—	How many values have failed to parse since the last Clear
failure	Signal	—	Fires once when a Parse could not read part of its input, or when the pending text exceeded Max Pending; Error Count says how many

Patterns

• Server-Sent Events data → chunk, onMessage → parse, format NDJSON: a log stream that arrives several lines per event.
• values → For Each items renders everything a chunk completed, instead of only the last value.
• pendingCharacters on a debug Text output makes a format mismatch obvious instead of looking like a dead stream.

Watch out for

• Using 'Single document' on a never-ending stream — the buffer grows until Max Pending trips.
• Reading only parsed when a chunk can complete several values; the earlier ones are then silently ignored.
• Adding this after Server-Sent Events when each event is already one JSON object — the SSE node's Data output has parsed it.

Examples

Long-running task monitor: progress, batched log lines, and a visible connection

A backend job streams two kinds of frame on one connection. Pattern Extractor pulls the percentage out of human-readable status text, so a progress bar tracks it without a Function node. JSON Stream Parser turns NDJSON log payloads into values — several may complete in one frame, so values rather than parsed is what feeds downstream. Stream Buffer batches those into a flush every 250 ms, which keeps a busy log from repainting the list hundreds of times a second, and the stream's onClose flushes the tail that never reached a full batch.

Related nodes

Server-Sent Events, Text Accumulator, Stream Buffer, REST

Generated

This page is generated from node-catalog-enriched.json. Do not edit it by hand — run npm run docs:nodes to regenerate, and fix the source enrichment instead.