Pattern Extractor

Pattern Extractor: pulls matches and capture groups out of text with a regular expression, without needing a Function node.

Runs pattern over text on each extract and publishes the first match, its capture groups (numbered and named), and — with Extract All on — every match. An optional group that did not participate becomes an empty string rather than a hole in the array, so downstream indexes stay stable. firstGroup is a convenience for the overwhelmingly common single-group case. A pattern that will not compile is a result, not an exception: ok becomes false, error explains, and the failure signal fires — distinct from notFound, which is a normal outcome. Note that a catastrophically backtracking pattern is still the author's problem; this runs the platform regex engine and cannot bound it.

When to use it

Extracting a value from text that is not structured data: a percentage out of a progress line, a tool name out of an agent status message, a field out of a log record. Prefer JSON Stream Parser when the payload really is JSON, and String Format or Substring for fixed-position work that needs no pattern.

At a glance

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

Inputs

Values

Name	Type	Default	Description
extractAll	Boolean	false	Collects every match into Matches instead of stopping at the first one
flags	String	—	Regex flags i, m, s, u and y; g is controlled by Extract All and a g written here is ignored
pattern	String	—	A JavaScript regular expression without the surrounding slashes; capture groups appear on Groups
text	String	—	The text to search

Signals

Name	Type	Default	Description
extract	Signal	—	Runs Pattern over Text and reports what it found

Outputs

Values

Name	Type	Default	Description
firstGroup	String	—	The first capture group of the first match, which is the whole answer for a pattern like (\d+)%
groups	Array	—	Capture groups of the first match; an optional group that did not participate is a blank string, not a hole
match	String	—	The first match, or blank when nothing matched
matchCount	Number	—	How many matches were found, which is at most one unless Extract All is on
matches	Array	—	Every match when Extract All is on, otherwise just the first
namedGroups	Object	—	Named capture groups of the first match, keyed by name

Signals

Name	Type	Default	Description
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 once the extract has run, whether it matched or not — Found and Not Found say which
found	Signal	—	Fires when the pattern ran and matched at least once
notFound	Signal	—	Fires when the pattern ran and matched nothing, which is an ordinary outcome rather than a mistake

Failure outputs

Name	Type	Default	Description
error	String	—	Why the pattern could not be used: it is blank, or it is not a valid regular expression
failure	Signal	—	Fires when the pattern itself is unusable, which is a bug to fix rather than a result

Patterns

• Stream text → text, pattern (\d+)%, firstGroup → Number → a progress bar.
• Named groups turn one pattern into several outputs without chaining extractors: (?<tool>\w+)\s+(?<state>\w+).
• failure → a visible warning during authoring catches a mistyped pattern that would otherwise read as 'never matches'.

Watch out for

• Parsing JSON with a regex instead of using JSON Stream Parser.
• Treating notFound as an error state — most streams contain lines the pattern is not meant to match.
• Building a pattern from user input without bounding it; nested quantifiers can hang the frame.

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, JSON Stream Parser, Substring, String Format, String Mapper

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.