parseRegexOutput

Extracts structured data from LLM text using regular expression capture groups. Supports both named groups and positional groups with explicit names.

Import

import { parseRegexOutput } from "flowneer/plugins/output";

Usage

Named groups (recommended)

const result = parseRegexOutput(
  "Action: search Query: quantum computing",
  /Action:\s*(?<action>\w+)\s+Query:\s*(?<query>.+)/,
);
// { action: "search", query: "quantum computing" }

Positional groups with names

const result = parseRegexOutput(
  "SCORE: 8/10",
  "SCORE:\\s*(\\d+)/(\\d+)",
  ["score", "total"], // maps group 1 → "score", group 2 → "total"
);
// { score: "8", total: "10" }

No match

const result = parseRegexOutput("no match here", /Action:\s*(\w+)/);
// null

Signature

function parseRegexOutput(
  text: string,
  pattern: RegExp | string,
  groups?: string[],
): Record<string, string> | null;

Parameters

Parameter	Type	Description
text	string	LLM output to parse
pattern	RegExp | string	Pattern with capture groups
groups	string[]	Names for positional captures (used when no named groups exist)

Returns null if the pattern does not match.

All captured values are strings — apply Number(), parseFloat(), etc. as needed.

Fallback Indexing

If neither named groups nor groups array is provided, positional captures are returned as group_1, group_2, etc.:

parseRegexOutput("foo 42 bar", /(\w+)\s+(\d+)/);
// { group_1: "foo", group_2: "42" }

In a Flow

.then(async (s) => {
  s.__llmOutput = await callLlm(`Rate the sentiment (1-10): "${s.text}"`);
})
.then((s) => {
  const match = parseRegexOutput(s.__llmOutput!, /Score:\s*(?<score>\d+)/);
  s.score = match ? Number(match.score) : 5; // default 5 if no match
})