Files
EVOLV/manuals/node-red/function-node-patterns.md
znetsixe 6a6c04d34b Migrate to new Gitea instance (gitea.wbd-rd.nl)
- Update all submodule URLs from gitea.centraal.wbd-rd.nl to gitea.wbd-rd.nl
- Add settler as proper submodule in .gitmodules
- Add agent skills, function anchors, decisions, and improvements
- Add Docker configuration and scripts
- Add manuals and third_party docs
- Update .gitignore with secrets and build artifacts
- Remove stale .tgz build artifact

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-04 21:07:04 +01:00

1006 B

Node-RED Function Node Patterns (EVOLV Summary)

Based on: https://nodered.org/docs/user-guide/writing-functions

Return Semantics

  • return msg; sends to output 1.
  • return [msg1, msg2, ...]; sends one message per output position.
  • Use null for outputs that should not emit.

Examples:

  • return [msg, null, null]; -> output 1 only
  • return [null, msg, null]; -> output 2 only

Message Mutation Pattern

  • Start with the incoming msg, set fields (msg.topic, msg.payload), then return/send.
  • This preserves message context unless there is a deliberate reason to create a new object.

Async Function Pattern

  • For asynchronous work, call node.send(...) and then node.done().
  • Avoid returning a message when output is sent asynchronously.

EVOLV Practical Rule

  • In example flows (including parsers), always align return-array position with downstream wiring.
  • For dashboard parser functions, keep one stable output mapping per metric to avoid wire-level regressions.